Step 1: When you are at any section of the forums, you will see the link bar at the top underneath the banner. You must click on it like so:
Step 2: Now you have reached your control panel. To your left there will be a lot of choices you can make, but for now just click on "Edit Signature" underneath "Settings and Options". This can be seen here:
Step 3: You will now reach this screen:
Similar to choosing an avatar, you now have lots of choices for choosing a signature. When you wish to use a signature, there are size rules and forums rules for them. Do not use large images, bright words, or anything that could be considered insulting to a race, religion, member, etc. Your signature will be removed if this occurs.
Now, you can upload images from a site or from your computer for usage in your signature or you could link to them using the following code:
Once you finish choosing your images or text, click "Save Changes".