Hello, and welcome to mp3car. This forum is primarily dedicated to the hobby of putting computers, in our cars! That being said, your question doesn't really relate to carpc's in any way, so you may not get much of an answer here. Your best bet might be to try an automotive electronics or security webite. I would hate for you to wait for an answer here when your question would be better answered on a more appropriate forum.
That being said, You need two relays. Both normally open. When you hit the button, you want each relay to momentary pulse on (Lock for lock, unlock for unlock). One relay would tie brown to ground, one relay would tie white to ground (Through normally open). If you can have your wireless relay box wires pulse both two different wires on when you hit different buttons, that would likely do what you need. Just tie each wire to each relay. That relay box sounds like it only has one channel (But you need two, one for lock, one for unlock).