Lay the fabric on the floor with the backside facing up. Center the frame on the fabric. There should be at least 2 to 3 inches of extra fabric on all four sides. If not, you need a smaller frame for your fabric piece.
Fill the staple gun with upholstery staples. Fold the excess fabric on the top of the frame up and over the frame. Staple it in place in the center of the frame.
Move to the bottom of the frame. Fold the excess fabric up and over the bottom of the frame, pulling it taught but not causing the fabric to wrinkle. Staple that piece in place in the center of the frame.
Fold the fabric on the left side over the frame, and staple it in the center. Fold the fabric on the right side over the frame, pulling it taught so the fabric is smooth on the front of the frame. Staple it in the center of the frame.
Move back to the top of the frame. Pull the next section of fabric taught and put a staple 1 to 2 inches from the center staple to the left side. Do the same on the bottom of the frame, then the left side and the right side.
Continue placing a staple every 2 inches to the left of the last staple, starting at the top of the frame and alternating sides. Do the same for the staples to the right of the center.
Fold the corners down and staple them into place. The fabric will then be evenly stretched.