You need to be sure you have a few things first.
1) HDTV receiver either from cable, satellite or built in
2) Home theater aparatus
2A) All in one receiver/DVD player or receiver
2B) 5.1,, 6.1, or 7.1 speaker system
3) proper cables
3A) DVI or HDMI for HDTV signal
3B) Digital optical cable for DVD player/receiver
3C) High quality cable for other compenets
3D) High quality speaker cable

If you have all of that, you are in business.

The goal of home tehater is to have your theater source, i.e. the HD content or DVD content to have its sound processed though the Surround receiver. So you would be best off using an optical cable from your HDTV sources to the Surround receiver. If its an all in one, then you only need a cable from the HDTV tuner/cablebox. If you have a separate DVD player then you would want two optical cables to the receiver.
Set up your speakers. Use the DVI or HDMI cable to connect your TV tothe receiver and you have a system.

As for placement, you put the center channel in front near the visual source, the left and right ront, well in the front and the rear where they belong.

If you have no already purchased hardware, for simplicity I suggest you get an all in one. It is a surround receiver/stereo/CD/DVD player all in one. Then you only need an optical cable from your tuner and the DVi to the TV.