You can first get in touch with the authority in charge and then find people who can connect you to community health workers who know best how to deliver health related messages to the community. This is because every location has unique characteristics and people have different priorities. In such a setting, face to face interaction would be appropriate hence word of mouth accompanied by pictures and demonstrations would work.

Here is my suggestion: work with the Ministry of Health to implement strategies for cooking salt enrichment from the available choice of manufactured salt
study the environment to know the soil of the region which is poor in iodine
find out the places that have more people sick with goitre and more children who are born with neurological problems.

All these elements will help you assist the population to understand the problem.

From Bradley Woodruff:

Dear Janny Goris:

Thank you for sharing this interesting finding. However, before pursuing potentially expensive program remedies, I would suggest some additional thought about the indicators used to formulate this very high estimate of the prevalence of iodine deficiency.

The two most commonly used indicators of iodine status are the presence and size of goiter and urinary iodine concentration (UIC). Goiter is an imprecise indicator and takes years to resolve after iodine sufficiency is achieved. This is why UIC has largely supplanted it; however, because of its wide fluctuations, a UIC from a single urine specimen cannot be used to determine the iodine status of an individual. Therefore, it cannot be used to calculate the prevalence of iodine deficiency. Unfortunately, it is a very common mistake to calculate the proportion of individuals with UIC values which fall below some cut-off. Even the WHO micronutrient database did this in the past, although I have been assured that this would be discontinued. This means that it is not possible to estimate the prevalence of iodine deficiency without using extraordinary methods, such as 24-hour urine collection, which are not normally employed in cross-sectional surveys.

We should instead follow the WHO recommendations which say to calculate the median UIC and compare that to some cut-off to determine the overall population iodine status. For non-pregnant women of child-bearing age and school-age children, this cut-off is 100 ug/L. This means that a population with a median UIC of 101 ug/L would be labeled as iodine SUFFICIENT even though almost 1/2 of the population would have a UIC less than 100 ug/L. This is why the cut-off of 100 ug/L should NEVER be used to determine a prevalence of iodine deficiency; it will automatically produce a huge overestimate if used this way.

In our survey in Papua New Guinea in 2006, we found a median UIC in women of child-bearing age in the Highlands region of 130 ug/L, thus defining women in this region as iodine sufficient. This is not to deny that the UIC in school-age children is worse nor to deny that there are foci of iodine deficiency within this region. Moreover, in the Highlands region, the median salt iodine concentration was 54.7 ppm, and only 0.5% of household salt specimens tested had iodine concentrations lower than 15 ppm. I understand that these results are quite old, but I am not familiar with anything more recent. Nonetheless, our survey does produce some evidence that iodine deficiency may not a widespread, severe problem everywhere in the Highlands of Papua New Guinea, so you may wish to give your results a critical second look.

Go Through the following links
Salt Iodization - Nutrition International
https://www.nutritionintl.org/what-we-do/by-programs/salt-iodization/

Through support from the Government of Canada, Nutrition International has been working for more than a decade to speed up the pace and expand the adoption – or scale up – of universal salt iodization around the world. We want to see universal salt iodization because not only is it the ideal vehicle to deliver iodine, it is ...
[PDF]Double FortiFieD Salt - Nutrition International
https://www.nutritionintl.org/content/user_files/2014/.../MI-DFS_Brochure-rev3.pdf

to date - Universal Salt Iodization. Award-winning research undertaken by the Micronutrient Initiative and the. University of Toronto, with financial support from the Canadian International. Development Agency and the World Bank, has resulted in the ability to enrich salt with both iodine and iron. The fortification of salt with ...
MI welcomes announcement of mandatory salt iodization in Punjab ...
https://www.nutritionintl.org/.../mi-welcomes-announcement-of-mandatory-salt-iodiza...

Jun 23, 2015 - PAKISTAN – The Punjab Health Department, with assistance from the Micronutrient Initiative (MI), has decided to bring forth legislation on mandatory universal salt iodization (USI). The adviser to the Chief Minister on Health, Government of Punjab, Khawaja Salman Rafique requested MI to support the ...
Salt iodization in Ethiopia - Nutrition International
https://www.nutritionintl.org/2009/04/salt-iodization-ethiopia/

Apr 2, 2009 - Working with partners such as the Micronutrient Initiative and UNICEF, they launched an ambitious project – the establishment of a Central Iodization Facility (CIF). The CIF, to be located in Afdera, will be a modern streamlined facility equipped with salt iodization machines and material handling facilities to ...
WFP and Micronutrient Initiative work to boost salt iodization in Sudan
www.ign.org/p142002498.html

In Sudan, 22% of the population is affected by Iodine Deficiency Disorder, the single greatest preventable cause of mental retardation. This condition affects children's ability to learn. WFP is working with the Canadian foundation 'Micronutrient Initiative' to help address this issue. Salt producers in Sudan are being helped to ...
Micronutrients | Nutrition | UNICEF
https://www.unicef.org/nutrition/index_iodine.html

Dec 23, 2015 - Fortification programmes are extremely effective in preventing micronutrient deficiencies at minimal cost – often only a few cents per person per year. Universal salt iodization and flour fortification programmes (to add iron) have provided successful mass fortification in many countries. Home fortification ...
Salt Iodization for the Elimination of Iodine Deficiency (Micronutrient ...
https://www.amazon.com/Iodization...Micronutrient-Initiative/dp/9070785137

Buy Salt Iodization for the Elimination of Iodine Deficiency (Micronutrient Initiative Series) on Amazon.com ✓ FREE SHIPPING on qualified orders.
[PDF]Reaching the rural poor in India with iodized salt: the Micronutrient ...
www.iccidd.org/newsletter/idd_nl_may11_india_rural.pdf

IDD NEWSLETTER MAY 2011 INDIA. Reaching the rural poor in India with iodized salt: the Micronutrient lnitiative's lodized Salt. Coverage Study 2010. Barbara Strange Micronutrient Initiative. Study report by Mathew Joseph, S Kaushik, Suvabrata Dey Micronutrient Initiative;. Sucharita Dutt, Ranjan Kumar Jha Micronutrient ...
'Micronutrient' Work To Boost Salt Iodization In Sudan - World Food ...
www.wfp.org/videos/wfp-supports-salt-iodization-sudan-prevent-mental-health-disoder

May 19, 2014 - In Sudan, 22% of the population is affected by Iodine Deficiency Disorder, the single greatest preventable cause of mental retardation. This condition affects children's ability to learn. WFP is working with the Canadian foundation 'Micronutrient Initiative' to help address this issue. Salt producers in Sudan are ...