Box or Google Drive as storage for nodejs webapp

I'm developing a webapp in nodejs that require the upload of some media and I'm deciding if using Google Drive or Box as storage for static media of my app.

Both solutions use oauth2 for authentication, but I can't understand how to connect my node app to a single account (where the storage must be). The problem is that I can't find in their documentation an example that fit my problem.

What I have to do to implements this? If it's not possible what are good cloud storage alternatives that offers free space? I don't want to pay for a service before of a production environment