The FAQ for Premiere Clip says sharing to Facebook is an option. I just installed PC and there's no Facebook option I can find. Also missing is save to Camera Roll.
Available options are: Save to Gallery, Creative Cloud, Publish & Share, Sendd to Premeier Pro CC, Share on YouTube, Share on Twitter
Version: 184.108.40.2061 on Android.
Sharing to Facebook is not an option in the current Premiere Clip version.
Sorry for the miscommunication! The FAQ is old, I'll update it.
Save to Camera Roll is for iOS (Apple devices) which is the same as Save to Gallery on Android devices.