Here is how the companion app can be useful, even if you don't have FCPX:
The app allows you to upload any file(s) to Frame.io without having to open a browser. Just use the pre installed Finder Service to send and upload files with the companion app.
- Select any file(s) in the Finder
- Make a right mouse click or ctrl+click -> the contextual Finder menu appears
- Choose Service > Upload to Frame.io
- The companion app launches and is ready to upload your files