Add iframe to Contact in Front page section

Hello,

I want to add an iframe (with Facebook code) to Contact in Front page section just under ‘Section Subtitle’. I tried to achieve this by edit ‘Contact Content’ but it doesn’t work, it also doesn’t want to work when I put code in ‘Section Subtitle’. What I found is that in inspection view of webpage when I add code just after <div class=”hestia-description”> it works as it should. So in which file should I add this code ?