Okay....well, look to the upper right corner of the forums.
Do you see
My Controls there? Click on it. Scroll down and you will see an option
Edit Signature. Click on it.
Open a new window and go to www.photobucket.com (or any other image hosting sites)
Log in to your account or make yourself a new one.
When that's done, upload the sig you want to use to the account.
Once it's uploaded, you will be given a URL. This is the URL for your sig. Copy it.
Come back to your
Edit Signature and type this into the box :
[ IMG ]Paste the URL you got from photobucket here.[ /IMG ]
(without the spaces)
Then click on
Update Signature and you should be done. ^_^
For example : this is my signature.
This is what I typed :
[ IMG ]http://i7.photobucket.com/albums/y291/yin-chan/yc0zn.jpg[ /IMG ]
This is how it looks like once I delete the spaces between [ and IMG.

Does that help?