1) From the file menu, click 1, 2, 3 as seen below

2) After clicking "show debug" this pop-up will appear. Click "Yes".

3) A button "unregister" will appear.  Click it.

4) Then click "Exit Outlook now". 

5) Once Outlook is restarted, follow the process to re-register your license. 

...or if you're transferring a license, then open Outlook on the computer where you'd like to transfer your license and finalize the process there.