Find the Left side lower half panel that has the hole in it for the power input and switch.

Mount the switch to the side panel with 2x M3x8 countersunk screws and 2x M3 nuts

Using 11x M3x8 countersunk screws and 11x M3 T-nuts install the left side lower half panel onto the printer

Using 11x M3x8 countersunk screws and 11x M3 T-nuts install the left side upper half panel onto the printer