Step 3: Taping the screen.
Cut some of the scrap vinyl into strips, and stick it to the screen and the frame so there is no empty space for ink to get through. Cover the fabric all the way around about 1.5" from the edges of the frame.
Start with the top of the screen, then do the bottom.
The vinyl might not want to stick to the fabric very well, which is where the heat gun comes in.
Once the vinyl is all in place, quickly hit it with some heat and burnish it flat to the frame and the screen with your fingers. The heat will set the adhesive of the vinyl and make it stick firmly to the frame and the fabric.