Sonic Electronix is an amazing distributor with excellent customer support. btw, make sure you get the Hifonics Brutus line, and not the Zeus.
It's literally just a plug and play type of controller, one end goes in the amp, the other is the knob that you control. The only difficult part is tucking away the wire from sight. Many people just run them through their car without hiding it though, which personally, I cannot stand.
Here's the simplest answer in terms of general knowledge for deciding what ohm load you need. If you're running 2 subs, you will want them both to be Dual 4 Ohm in order to achieve a 1 Ohm load. If you're running 1 sub, you'll want a Dual 2 Ohm in order to achieve a 1 Ohm load.
You don't HAVE to run at 1 Ohm, but that Power Rating you see on the Hifonics Brutus 1200.1 amp, for example, is measured at 1 Ohm.
Subwoofer wiring guides are very easy to find online, just google them if you need a little more detailed description.