It's pretty intuitive.
If it mounts at the TOP/REAR then face the internal fan DOWN unless you have a TOP exhaust/intake in which case flip it the other way.
Attach the screws.
- the main cable attaches to the motherboard (20 or 24-pin)
- each drive gets the proper cable
- the CPU may have a 4-pin or 8-pin connection next to it you need to attach
- if a graphics card has a 6-pin/8-pin connector they must be attached.
Do all this with the POWER SWITCH OFF, then connect the cable, flip the power switch and standby to turn it off quickly if you smell anything or see sparks.
Also, keep the cables clear of any fans. Tie wraps may help.