Is there a browse button you can click? I don't use Google drive, but with most file upload online programs there is a "browse" button, I click that, and that will bring up a file selection dialogue screen (like if you were to go to File -> Open in Excel). Once that screen is open:
Send keys for the path and {Enter}...this will bring you to the folder of the path
Wait (1)
Send keys for the filename and {Enter}
Then click OK/Open/Upload, whatever the next steps are.
Good luck!