how do i hook up this relay?

It's used for disarmactive output 300ma (-)

Description they gave me:

this feeds negative output at normal time.  but during arm mode or remote engine start or immoblize mode, this stops any output and with the additional relay it disables ignition coil.

it's a 12vdc 30/40A relay...i don't know anything about relays...

How do I hook this up??

Ok it would help if you would tell us what kind of alarm or remote start or whatever. Manufacturer and model number. Also what Year, make, and model vehicle your putting it in.  

It's a not a branded alarm.  It's called the VT-v12 2 way RS/Alarm.

Here's the colors and description again...

BLACK/ White: disarmactive output 300ma (-)

Looking back on the wires I get these colors...

     |      (blue)

the colors dont really hae any significance.  what function are you trying to create, as in what are you trying to power or isolate ect...

the most common use for a relay is to drive a high current device that a brain cant.  usually a brain will be able to supply a (-)200mA signal for whatever function.  basically the brain can ground the function but not supply the power to drive it, like 10 amp headlights.  85 is usually the gound and activation wire.  take that to the (-) on the brain for said function.  from there take 86 and 87 to 12v constant and pin 30 will output 12v when 85 is allowed a ground from the brain.  87a isnt used much for most basic connections.  basically 86 and 85 are the controll circuit to allow high power to go from 87 to 30.