Are you saying that you have an IR repeater that sends the IR signal to the other room? Or are you using the RF extender that comes with the 890 and it sends the IR signals to the equipment?

As for controlling it - does it have a separate remote or is it controlled from the Onkyo? If it has a remote then you just add it like any other device and you control it just like you're controlling the Onkyo - IR repeater or use the RF extender. If it's controlled by the Onkyo then just treat it like any other device - DVD player, etc.