Buy a gryphon ride to Sentinel Hill from the gryphon master Dungar Longdrink, then take Osric's Crate to Lewis at Sentinel Hill.
The gryphon master in Westfall is Thor. If you've spoken to him before, then you can take one of my gryphons to him.
That's a good lesson to know: gryphons are always trained to fly to their capital city, but they'll only take you to a remote gryphon master after you've already been there.
You've already been to Thor, so just speak with me again when you're ready to take a gryphon to Westfall. Once there, you can deliver Osric's Crate to Quartermaster Lewis.