ADA compliance, adding alt text to navigation FA icon/image links

We are working on ADA compliance, WCAG 2.1 for our website. As a preliminary check, I scanned a few pages on our site and found a few errors that I need some help knowing how to correct. The errors have to do with navigation links, specifically the built-in social media images (at top and bottom of each page on our site), the search image (magnifying glass) in the header, and the scroll-to-top button that appears at the bottom of each page when scrolling. Those images appear to be FontAwesome icons which are hyperlinked, but contain no alt text, which throws a compliance error. I do not know how to add alt text to those images since they are not in the “Media” section of WordPress. How can I add alt text to these image links?

Website: https://www.bankersinsurance.net/
Compliance test tool I am using: http://wave.webaim.org/

Thank you for your help!

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