Build the frame. Put the stretcher bars together, and put a couple staples in the corners for added strength. Check to see if the frame is warped by measuring the diagonals. The measurements should match, if not, you can use a rubber mallet to tap the frame into squareness.
Place the print face down on a clean and clear surface. The print most likely will get scratched if the surface is not clean.
Measure 5 inches in on every side of the print. Make two small marks on every side to act as a guide for making sure the print is centered. Use a pencil to make light marks.
Add the frame to the print. Line up the frame on the marks you made.
Start with one of the longer sides. Do not stretch it yet, fold the print over the back and attach with staples. Hold the staple gun flush against the print. Squeeze the staple gun while exhaling. Make sure the print lays flat, if there are wrinkles, it might show through in the final piece. Place each staple 2 to 3 inches apart.
Turn the frame 180 degrees to the other long side. Stretch the print gently so that it is tight, but not as tight as a drum. The point is for it to be flat. Then, put a staple in the middle of the side. Work your way to one corner, then go back toward the other while maintaining the tightness of the stretch.
Attach the sides. Pull each side tight so that there are no wrinkles. Start in the middle and work toward one corner, then go back and do the same.
Stand up the stretched print on the table. It will make folding over the corners easier.
Make neat corners by folding the print around itself. Pull the print tight and fold it against the top edge of the frame. There will be a 45 degree triangle of excess. Fold it in half and tuck it under the first fold. It should be flat. Secure it along the back with two staples to hold it in place.
Repeat for each corner, and check your work as you go.