Locate the studs over the doorway with an electric stud finder. Mark the studs on the wall.
Center the pull-up bar over the door so the mounting brackets rest over the center of the studs. Mark the mounting holes on the bracket on the wall.
Select the largest-diameter lag bolts that will fit through the mounting holes and select a drill bit that measures half the diameter of the lag bolts.
Drill the holes into the studs with the drill bit at the marked locations.
Place the pull-up bar over the holes and drive the lag bolts into the wall with a socket and ratchet.