Sign in to Office online
Go to the Office web page, and in the upper right-hand corner select Sign In to sign in with your Office 365 work or school account.
Lightweight versions of the Office apps are available right there. Just click an app icon to start using the app in your browser.
And if you don't already have the desktop versions of the Office apps installed, select Install Office near the top right of the window.
For more details, see Sign in to Office Online.