Your signature is automatically generated using the software Exclaimer.  It should show automatically when you create a new message.  If this doesn't happen follow the steps below.

1. When creating a new email, click the ‘Signatures’ button.
2. Click ‘Signatures’ in the drop down list.

A list of available signatures will be shown at the left hand side of this window.

Use the ‘New messages’ drop down menu to select the signature to be used. (You may only have 1 option!).