Do you still have the manual for your receiver?
You're going to need to go into the config menu and set it up for a subwoofer. This will require you to tell the receiver to send bass to the subwoofer, at which point you have some decisions to make. You can have it so that only the subwoofer plays bass, or you can have your subwoofer play bass along with your main speakers. This is changed by choosing the speakers as "small" or "large" [small speakers do not play bass].
You'll also have to set at what frequency you want the receiver to send to the subwoofer, this is done by changing the crossover point.
I believe your receiver has built in autosetup, so all of this could be done by plugging in the microphone and letting it do it's magic. You can always adjust from there. [Running this will also have your receiver apply equalization automatically which you may choose to disable later].
