Listing Layout that pulls in value of custom field

Hi. I have folks submitting their listing and I want to allow them to add their social media profiles (facebook, twitter, Google+, etc.) I have set up custom fields for these. But what I would like to display instead of the URLs to their social provides is an icon that links out to their social profiles. So if they give us their twitter profile link, I’d like to code the listing page to show the icon programmed with the link being the value of the custom field.

I can’t find any documentation on how to pull in a custom field in the listing page template. Is this possible? Has anyone done this?