Ensure front outlet is perfectly level. The recommended installation height is 800 to 1000mm from the water surface. Seal around the outlet to prevent possibilty of any leakage back into the wall.
Fit valves to each inlet and ensure tubing length is identical to all inlets.
Install your pump. Ensure its correctly sixed!
Pump prefilter on in-line strainer must be installed to prevent leaf particles etc. from entering the waterfall.
A steel lintel must be installed for any wall or load-bearing structure built above the waterfall.