If it's a picture you took, you have to upload it to photobucket or something like that.
You need the direct link, like what would show up where you would normally type, "www. whatever." You need that link.
Come here, click on the "img" button when you go to post something, paste the entire link there.
Click preview to make sure it works. If you're doing it from your phone, delete the default "http" that shows up, there's already an "http" in your link. If you don't, it'll mess up and won't post the pic. You'll get a red X or whatever.