He gets all of his supplies at craft stores (like Hobby Lobby), and his frames from everywhere!
First you center the ironed stitching (yes, carefully iron it!) on foam board. He uses white or black - depends on how it looks behind the picture. Black makes it darker, but can be useful when there are lots of threads on the back side, showing through light colored fabric.
He does a few on one side, then switches to the opposite side, pulling the fabric tight each time. He does a few pins in each side in this fashion. That way he can make it closer to evenly stretched.