How do I get a character card onto my signature?

I've seen these lately and downloaded a couple but I can't get them onto my sig. Help an Elezen out.

"My profile" is in the upper right, next to the logout button.
From there you can edit your signature.

Uh, it's Settings, not My Profile. Sorry!

I've tried that but it seems the picture is too large (It's in .png when I download them).

EDIT: Managed to find a site that has a similar design. This should do.