If you bought Office through the Microsoft Store If you bought Office through the Microsoft Store, you can enter your product key there. Go to www. In the upper right-hand corner, select Sign in and enter the user ID and password you used to buy Office. After you sign in, select your name in the upper right-hand corner, and then select Order History. Locate the Office one-time purchase or individual Office app, and then select Install Office to view your product key this doesn't actually install Office. Select Install Office again in the window where the product key appears. On the Hi.