you need a wiring harness to tie it all together
A)
87 : It's the power output that goes directly to the ballast (put an in-line 15A fuse in this line between the relay and ballast). This basically is power coming straight out of the battery and thru the relay and to your ballast so use heavy gauge wire like 12AWG or similar.
B)
86 : This is basically a ground wire for the circuit or relay. I just hooked up my negative terminal of the battery to this but others may suggest that you find a quality ground on the chassis. Try the chassis but MAKE SURE it's a quality ground. If not, it may appear like it's working but you may get intermittent problems with a faulty ground. If not sure-start with the battery.
C)
85 : This goes straight into the hot lead that turns on your low beams. Use a tester and find out which lamp going into your low beams (before it was HID) goes on when you turn on your headlight low beam switch. This is the one that you can use an in-line splice or find a way to solder this in place. This will simply tell the relay (when you turn on your low beams from inside your car) to pull current directly from the battery. This is why it's important to do this. It's a very simple design yet ingenious in many ways. You can still incorporate your OEM headlamp switch but not stress out the wiring associated with it.
D)
30 : You connect this straight to the positive terminal on the battery. The relay and positive terminal on the battery you MUST put a 30A fuse in-line. If you don't you defeat the whole purpose of this setup.
**Unless you have one relay for each ballast then it's just 15A main fuse**