This page will show you how to create and edit a signature in the desktop application for Outlook (both Office 2019 and Office 365).
Select the Mail tab from the left hand side. In the center pane, click on the Signatures button. This will open a new window where you can create a new signature.
You can create as many signatures as you like for whatever roles you fill. On the right, you can select which signature to use when sending, replying, or forwarding an email.
Don’t forget to hit OK to save your changes.