Find the settings button (small gear icon) in the top right of the Outlook page. Open All Outlook Settings. This will open a new window.
Step 3:
Navigate to the Mail tab on the left hand side, then to the Compose and Reply sub-menu option. In the center pane, the first box at the top will be where you can compose and edit your email signature.
There are two options underneath this to select when to automatically include your email signature (when composing new emails, and/or when replying/forwarding).