If you have the intercom, you should have (somewhere behind he triple tree or under the shelter) a connection for the riders helmet. There is also a connection that comes out near the rear of the seat on the left hand side for the co-rider.
You'll need both helmets fitted with the speaker/mike of your choice (both the same is always best)and then the appropriate lower connects that hook into the stock Honda connections.
Assuming that all the wiring is good to go, that's all ya need!
The intercom is SO nice to have - makes talking to each other a breeze. No shouting involved.