Well If you have made your own image that you want to use as your own signature all you need to do to use it is this:
1. create an account on an image hosting website (personally I find photobucket.com is the best)
2. upload the image onto your account
3. then save the text in the selection box that has [img] at the start of it.
4. copy the text
5. enter your profile on this site and then click on signature.
6. paste the onto the ain bar and then click 'save'
and there you go you have your sig!!! ^_^