Acura TSX keyless remote?

I just purchased a 2007 Acura TSX and was surprised to find that it didn't come with one of those keyless entry remotes. Even my 2000 Honda Civic came with one. My question is what are the steps I have to take to get this in my car? I don't really know how these remotes work.. Do I have to just buy one of the remotes or do I have to buy additional hardware as well that sends the signal from my car, or is this already built into the car? Thanks!