Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
A new PC includes win but not Office except as a trial, or if your PC maker explicitly stated that it included a 'free' 365 Personal subscription, and if that was the case there would have been instructions on how to activate it with an MS Account.
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Re-set what password, a mail account password?
Did you create an MS Account and can you log on to that account?