You can now access Microsoft Office Online for free.
Go to: http://office.com
Log into your Microsoft account. If you don't have one, you'll need to create one. On the Office home page, you'll see:
Simply click on the app you want to use and it opens. Make sure NOT to select either "Install Office" or "Buy Office 365".
Note: you also have 5GB of One Drive storage space included, which is where your files will automatically be saved unless you specifically download them.