Design how you want your signature to look, putting links in it by adding brackets [[ ]]
Select it and click the HTML tab and copy the code of your text into the signature box mentioned above.
Be sure not to copy the tags at the beginning and end of the code that say <p> </p>. Or...
Adapt someone else's signature
Find a signature you like
Click edit this page
Copy and paste the signature into your signature box (see #1 above), but change all the links to your links: you do not want your signature leading to someone else's user page!
Do not use images, templates, or external links in your signature. Please ensure your custom signature complies with the relevant guideline. Use special code for displayed pipe character.
Done
