Disconnect the gun from the air supply, and ensure the nose is pointed away from yourself and others as you load it. Wear goggles just to be safe.
Press down the latch handle, and hold it down as you slide the magazine cover backwards.
Insert the strip of nails into the magazine with the heads of the nails positioned toward the top.
Slide the cover forward over the magazine so that the latch snaps and locks the cover in place.
Reconnect the air supply, and continue using the nailer.