If RingCentral FaxOut is not yet an added application on your box account, RingCentral FaxOut will not appear as an option.
Go to https://www.box.com/. Log in to your Box account.
Alternatively, you may log in using your Google account.
The sign in link is at the bottom part of the page.
Click Files to see the available documents.
Select the document to fax. Click the More Options button which is at the right side of the file you want to fax. Hover the mouse over More Actions. Click Add Applications.
Type "ringcentral" on the search box, then press Enter.
Click RingCentral FaxOut on the search results page.
A confirmation window will show up once RingCentral FaxOut has been successfully added to your Box account.