Box, Open Office documents in Office 365 Online
Install the "Box for Microsoft 365 for Web" app
Open a web browser and sign in to box.illinois.edu
Click on the "Apps" shortcut on the left-hand menu and search for "Box for Microsoft 365 for web." Alternatively, visit this link to view the "Box for Microsoft 365 for web" app.

Once the app page is open, if the blue button says "Remove," you already have it!
See an example

Select the "Add" button and confirm your choice when prompted to provide permissions


Open Office documents from Box
Once the app has been installed, open any Word (.docx), Excel (.xlsx), or PowerPoint (.pptx) file in Box
In the toolbar, select "Open"
Choose "Open in Word/Excel/PowerPoint Online"

Make your changes to the document; they will automatically save
Close the Office Online tab when your changes are complete
The Box preview will detect the changes and prompt you to refresh the page

That's it!