Slide the support tubes of the frame assembly of the mower bag, if it has one, into the holes in the bag fabric on the open end of the bag. Slide the frame in until the square part of the frame sits flush with the end of the bag.
Lift up the back cover on the mower, which is on hinges, to expose the underside of the mower.
Place the mower bag on the back of the unit, resting the frame assembly in the clips on the back of the mower. Attach the hooks on top of the frame assembly to the bar running between the mower handles.
Let go of the back cover of the mower and let it rest on the bag.