Adding photo to site meta data?

I’m new to Ghost and not a developer either, so working through a lot of beginner issues.

One problem I’m having is adding a site logo or photo to the site meta data? Right now when I share the site link in chats such as Discord or FB Messenger, they have an embedded drop down for links to show the site media, but mine is just empty.

When I go to the meta data edit section under the Ghost admin, my only options are to edit title and description?

Any help is appreciated! Thanks!