If you have a tripod, put the mic on it in the main listening position. If you're really ambitious move your sofa out of the way. If you don't have a tripod, you can put the mic on the back of your sofa; it's not the best solution, but it will do a decent job in many cases.
And also check all the speaker wires at the receiver end. Most calibration systems will tell if you there's a wiring mistake, but it's a good idea to double check first.
Plugging in the mic may automatically bring up the first screen on your display. Otherwise, navigate the onscreen display (or the display on your receiver) to start the auto setup program.
After starting autosetup the screen looks like this. You'll want to leave the room so you don't have to listen to the annoying test tones and so you don't affect the test tones hitting the microphone.
After the first round of test tones some auto setup systems will ask you to move the mic to additional positions in the room. This is usually to optimize the sound quality for multiple seating positions.
After the setup concludes, some receivers will ask you review and confirm the settings. If you've done everything right, this screen should mirror your home theater configuration.
If your receiver offers auto equalization (such as Audyssey), you may have to "turn on" that feature for it to be activated. Auto equalization may or may not actually improve your sound quality, so it's worth experimenting to see what you like better.
When you're done, just unplug the mic. Your receiver should be setup properly for surround sound in your room.
If you're at all technically inclined you might want to forgo the auto setup and tackle manual speaker setup. It's not all that difficult, but you should use a sound pressure level meter, such as a Radio Shack 33-4050. You'll probably do a better job yourself than the auto setup.
