1. Click the "My Matrix" tab, then click the "Settings" link
2. Click on the 'Email Signature' link underneath the My Information section.
3. Type in your email signature and click the "Save" button.

Your email signature is saved and will appear on every email you send through Matrix. You may go back and change it at any time. Also, on every email you send, you have the opportunity to change the signature just for that email.