Either You need a DVD-burner and iDVD on Your Mac Air - as it usually is extra
or You need an external hard disk
• must be Mac OS Extended (hfs) formatted - nothing else works for VIDEO
• should be a FireWire one - IF Mac Air got a FW-connection else use USB2
or connect other Mac - set in Target mode - so it works as an external hard disk
(also needs FireWire to work)
move project and events WITHIN iMovie Application - NOT on DeskTop/Finder as this will destroy it and iMovie loses connections to project and events. Very hard to repair to impossibly.
Yours Bengt W