How do I change the thumbnail from my link to my site?

[SimplicityBJJ]

When I post my websites link, a thumbnail preview appears. Im not sure what this is called. How do I customize this to what I want it to be?

[JoKi]

Are you talking about the "favicon"? If so, have a look here.

https://community.weebly.com/t5/Site-Editor/How-can-i-put-a-logo-icon-in-my-website-that-appears-at-...