Normally Sharepoint and OneDrive are the only Cloud providers visible in Office 2016. To add Dropbox and Google Drive follow the following instructions:
Install the Dropbox client for Windows.
Click the system tray icon, and choose preferences, “Show Dropbox as a place”
For Google Drive:
Download a plugin from here.
Joel G Mathew, known in tech circles by the pseudonym Droidzone, is an opensource and programming enthusiast.
His favorite pastime is grappling with GNU compilers, discovering newer Linux secrets, writing scripts, hacking roms, and programs (nothing illegal), reading, blogging. and testing out the latest gadgets.
When away from the tech world, Dr Joel G. Mathew is a practising ENT Surgeon, busy with surgeries and clinical practise.