You will need 6 brackets for the base and 3 for the top. Place the M3 screws and bolts in place before you slide in the open beam. These brackets have a 0.5mm 'breathing' space between the open beam and the part itself on all sides.
Power Supply Brackets:
The shorter brackets are for the front, while the longer ones are to be set diagonally
Heat Bed Brackets:
It may not be obvious, but 2 of them are shorter than the other 2. The longer ones go in the front, while the shorter ones go in the back.
This will require you to remove 2 screws to the side of your PS. One of the screws taps into a internal heat sink. Be very careful because putting back the screw may be difficult if the heat sink is dislodged. You may need to stick a non conducting probe in to hold the sink in place. Make sure you unplug the PS and wait for the capacitors to be completely discharged before handling the PS.
This is for the reprap discount LCD panel. no screws needed! just slide it into the beam. Do not put this on the bottom most beam because it is slightly protruded and will hit the floor. It's meant to be attached on the same beam as the heat bed's mounts.
Get some M3x8 screws and mount the nema 17 to this plate. Then mount this plate to the brackets.