description of site when linked to

[marchonknoxco]

Hello. When I post a link to my site, the preview looks like this:

My Site Title
The basic Indivisible website beta, etc
mysiteaddress

and then no image.

I've changed the description at the top of my github page to ...

Knox County citizens resisting the Trump agenda — one step at a time. March on! http://indivisibleknoxcounty.org/

Is there something in the code that needs to be changed? If so, I can't find it ...
https://github.com/marchonknoxco/marchnoknoxco.github.io

Thanks!