Well don't feel bad. Plenty people have a problem
Once you have chosen your ticker and added the details it gives you an option of 3 codes. I never remember which one to use, so I always keep the window open and minimize it once I have selected and copied the code. I think it is the URL one. Then go into your profile at the top of the screen on the right and on the left of your profile page you will see edit signature. You go into that and simply copy and paste the code in there. Underneath to the right you will see an option to preview your signature. Select that and if you don't see your ticker, delete the code, go back to the ticker page you minimized and select another code. I am pretty sure it is the URL but can't think offhand. I have done several tickers and usually mess it up on the first try.
