Hopefully you can download an owner's manual to help you with your questions, but I will assume you have:
1) Master Volume switch. Use it only to help "blend" the subwoofer with your mains. Turn it up to the point you are happy with it, but you should not hear the bass coming from the sub it should be non directional.
2) A Cross Over Switch. As you are using the RCA connector from the LFE output on the receiver, you should have this turned off or set to the lowest level.
3) A Phase Switch. 0 - 180 degrees. Assuming you probably have the sub up front with your mains, set at 0. The phase switch helps to assure your woofer on the sub is moving in and out "in phase" with the woofers on your mains to avoid cancelling out.
Hope that helps some.