IBM Power System 9040-MR9 Manual page 94

Figure 81. Installing the front cover
6. If applicable, open the rack door at the rear of the system.
7. Replace the power supplies:
a) Slide the power supply into the system until the latch locks in place.
b) Repeat step "7.a" on page 80 to replace the remaining power supplies.
80 Power Systems: System backplane