To activate Office 365, open an Office 365 application on Swizznet (typically Excel or Word).
Next, you will be prompted to log into Office 365. Enter the email address associated with your Office 365 account.
If you do not get the login prompt for whatever reason, you can bring it up by clicking your username at the top right of the Office app, and selecting Switch Account.
Finally, enter your Office 365 password at the next prompt to finish activating.
You can then verify at any time that Office has been successfully activated by again checking the top right corner of the Office app. It should show you logged in as the email address associated with your Office 365 account.