Office Activation Guide (redeem.microsoft.com)

Go to login.live.com

Sign in to your existing Microsoft account, or create a new one (needs to be a personal Microsoft account, not an organization account).

Go to account.microsoft.com/billing/redeem

Paste your 25-character product key into the box, make sure the account the product key will be added to is correct, and click next.

If you see an error saying “This code has already been redeemed“, skip to step 4 of this guide.
If you see an error saying “You are not logged in. Please login before redeeming a token“, click here for a guide to resolve.

Confirm the product is correct, click confirm.

*There are no refunds after clicking confirm, this is due to the key being consumed and the license being permanently tied to your Microsoft account.

Go to the subscriptions tab of your Microsoft account, you will see your redeemed software listed, along with the date it was added to your Microsoft account.

Click the install link on the right-hand side to download the software.

Choose the language and version you wish to install then click the install button to download.

Before installing your new Office suite you should fully uninstall any old Office suites on your computer. Old Office installs are known to cause conflicts with a new installation, Office 365 in particular will attempt to override your new install.

Links to the Microsoft uninstall guides:
Uninstall Office on Windows PC
Uninstall Office on Mac

Double-click on the Office installer that was downloaded to your computer (most likely in your downloads folder) and follow the on-screen instructions.

Your installation is complete when you see the message “You’re all set! Office is installed now”.

Upon opening an Office App for the first time you will be asked to sign in to your Microsoft account, and sign in to the same account you used in step 1 of this guide, as that is the account the license is tied to.