How to Select Your Signature - Outlook Desktop
Compose a New Email.

Select Signature from the New Mail Message Outlook Ribbon and then click Signatures…

This will open the Signatures and Stationery window.
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Find and click on your preferred Signature File.
If you do not have a signature created, you may click on New and then define your signature in the body box at the bottom
In the New Messages and Replies/forwards select your desired Signature files to be used.

Your preferred Signature(s) will now be selected whenever Composing or Reply/forwarding.