and before you do anything else, it's best to upload your signature on imgur.com or tinypic.com (so open up a new tab)
I personally prefer imgur.com though! So once you upload it there, make sure you click on the photo that way it leads you to a url link that ONLY shows your sig and nothing else. Then copy that URL link and go back to the tbt tab and make sure you have [ img ] -insert sig url here- [ /img ] (erase the spaces in between "img" and the "[ ] " )
It should work after that! c: Make sure you "preview" it first to see if it shows up for you then save it! XD