Open the Office app. On the Account screen, tap Sign In. On the Sign In screen, type the email address and password you use with Office. This might be the personal Microsoft account you associated with Office, or the username and password you use with your work or school account. Open the Office app. On the Recent screen, tap Sign In.Can I download Office 365 to my computer?
Use the same email ID which you used to buy Office 365 personal subscription. Now click on your account & then click on My account. In Install section, click on Install button to download Office 365 setup. Once setup downloaded run the setup. After that setup will automatically install Office 365 on your PC.