There should be a round plug on the back of your radio. The trainer port. It will plug into that. If your radio does not have one(I don't recall ever seeing one with out it) then you can't hook up your radio to the computer(easily, at least).

If you do have the trainer port. Find the cable that's for your radio(Futaba,AirTronics,HiTec,JR, etc). Then you should be good to go.

If you don't have a trainer port. I'm sure there's some way to hard wire it. But I wouldn't know where to begin with something of that caliber.