Open Outlook Web App (OWA) and log in with your NetID and Activie Directory (AD) password.
(Please make sure that your Outlook is not open at the same time.)
Click "Options" at the upper right corner and select "See All Options..." from the drop down list.
By default, "Account" is selected. Click "Settings". Under "Email" category, you'll see "Email Signature", type in your signature and format it in any way you want.
Check "Automatically include my signature on messages I send" (if you want to include the signature in all outgoing messages), then click "Save" button at the lower right corner.
A text box "Saving Information..." appears briefly indicating that Exchange is saving your settings, after it disappears, click "My Mail" at the upper right corner.
You'll be back to the Inbox. From now on when you compose an email (create new, reply, forward, etc.)
If you checked "Automatically include my signature on messages I send" option, the signature is automatically included in the new message.
Otherwise, click "Insert Signature" icon to insert the signature.