To create or modify the signature that will automatically appear beneath your forum posts, click on your username in the upper-right corner of the screen, then click on "Account Settings".
Click on the "Signature" option and you will be presented with a text editor that will allow you to write and format your signature.
When you are finished, be sure to click the "Save" button to apply your changes.
Some restrictions apply: your signature may contain no more than 3 links to