How do I change the signature?

This is directly from the Microsoft Office Support pages

http://office.microsoft.com/en-us/outlook-help/change-an-email-signature-HA010156014.aspx?CTT=5&origin=HA010210657
Change a signature

1. In a new message, on the Message tab, in the Include group, click Signature, and then click Signatures.

Note To add your signature when replying to or forwarding a message, the signature options on the Message tab become available after you click Reply, Reply to All, or Forward.

1. On the E-mail Signature tab, in the Select signature to edit list, click the signature that you want to modify.
2. In the Edit signature box, make your changes to the signature.
3. To format the text, select the text, and then use the style and formatting buttons to select the options that you want.

Note These options are not available if you use plain text as your message format.

1. After making your changes, click OK.

Note If you want your changes to appear in the signature in a message that you currently have open, you need to update the existing signature. On the Message tab, in the Include group, click Signatures, and then click the signature.
Tip You can make changes to signature in a message that you currently have open by editing the signature in the message body. However, these changes will not be saved for other messages.
Change the signature included in an individual message

1. In a new message, on the Message tab, in the Include group, click Signature.
2. In the list, click the name of the signature that you want, and then make changes directly to the signature in the message.

1. In a new message, on the Message tab, in the Include group, click Signature, and then click Signatures.

Note To add your signature when replying to or forwarding a message, the signature options on the Message tab become available after you click Reply, Reply to All, or Forward.

1. On the E-mail Signature tab, under Choose default signature, in the New messages list, click the signature that you want.
2. If you want a signature to be included in message replies and in forwarded messages, in the Replies/forwards list, select the signature. If not, select none.