Determine the point on the pipe where you must institute a 90-degree bend. For the sake of example, the 90-degree bend must take place 25 inches from the left end of the pipe.
Measure 25 inches from the left end of the pipe. Mark the spot with a permanent marker.
Measure 6 inches back to the left from the 25-inch mark. Mark this spot with a permanent marker. Measure 2 inches back from the second mark and again mark this spot. You now have three marks.
Slide the pipe into the bender until the third mark -- the mark closest to the left end -- is at center on the bender. Bend the pipe upward to a 30-degree angle.
Slide the pipe until the second mark is at center on the bender. Bend the pipe up another 30 degrees.
Slide the pipe back until the first mark -- the initial 25-inch mark -- is at center on the bender. Bend the pipe up the final 30 degrees to complete the 90-degree bend.