Selecting this icon will bring up another window which allows me to select either Documents, Photos, Dropbox, and Box. The issue, however, is when I select the Documents option. The selection always shows an empty folder with a message "Documents imported from email or other apps will be stored here. You will be able to use them for faxing."
I've had this same problem since I've had ring central. It irritates me to no end. My son figured this out. The only way I could send was from desktop. I used to be able to long press on the document in my phone and it would bring up the rc phone app as an option to use and attach it to a new fax but now that is not an option like the person above says. The rc phone app prompted me to download the new ring central app which is a way to connect with other ring central users, this app shows up when I long press on a file but tries to create a new group to send to and there is no option to switch to a fax. I finally did figure out a way (Android), you have to clear the default app in your phone for the type of file you are using, for example if Adobe is set as the default app for opening PDFs you have to go into settings-->apps-->Adobe acrobat then click on set as default and click clear defaults. Then you can go click on the file you need and since there is no default app to open PDFs, it will give you the option of using the rc phone app and will add the file to your documents tab in the rc phone app. The developers REALLY need to fix the app and add a "browse" button that launches the file explorer to select the files you need.
Chris Archer is correct. I have the same problem described here on my LG v30 and Samsung tablet. And I've tried pasting from my document to the cover page when it's only one page. But that doesn't work either because of the limit on the number of characters for the cover page! I'm a software developer. Sometimes the apps I see out there just boggle my mind. RC probably paid someone a lot of money for a crap app. If i have to resort to logging in to the RC website from my mobile device, or changing default apps to open a document, then as far as I'm concerned, RingCentral doesn't provide a fax option for mobile devices. Faxing was the ONLY reason I purchased the app. Would love to find one that 1. supports browsing to document, 2. Has more intuitive interface, 3. Isn't so cumbersome to setup (option to allow sending from ANY email address). If I change my email address, I shouldn't HAVE to change that in my app. Send from one email account and receive on another? I'll probably switch to a different app. And then give RC a bad review.