If you need to change your Office license, in many cases you won't need to uninstall Office and reinstall. You will sign out of the current account and sign in with the new account or enter the new product key.
If activation fails, see Unlicensed Product and activation errors in Office. If you Office applications show two licenses, follow Step 4 in the article to remove the licenses and sign back in with the correct license.
These Office.com articles contain additional information:
How to Activate Office: