Tools|Account Settings|{select account}|Composition & Addressing

Tick the check boxes to add your signature to replies and forwards as required.

Thanks, I found it. The signature was already there but not on top of the reply but below the original e-mail.

Is there a way to have the signature show up with the reply? My replies are above the original email but the signature is way down below. I'd like to have it where the recipient would see the signature without searching. Thanks.