Adding fuelly to signature

I am having trouble doing this. I read the how to: Either I am copying the wrong thing from fuelly or I am trying to add it to the wrong place in the signature. I am copying the address when I go into Fuelly :
Eco (Chevrolet Cruze) | Fuelly. When I paste this in one of the link areas in the signature I get a message "invalid file". Anybody have an idea of what I am doing wrong? Probably obvious I am a "techy". I need exact instructions. LOL