JY, welcome. If you have the speakers for a 7.1 setup that's what you can use; TV isn't necessary for that. For example, you can use DPLIIx to steer ambient sound to all seven speakers even when playing two-channel material.
The general idea is to have the main speakers separated by about as much as your distance from them. The side surrounds should be about 6' up and directly to the sides of the listening position. The back surrounds also about 6' up on the back wall and separated by about as far as they are behind the listening position.
As for the sub, although the best location is often a corner behind the main speakers, when the room is square this results in exciting the length and width resonances at the same frequencies, with a likely boomy result. So, the sub should be moved out of the corner, possibly to the middle of the front wall, where the room resonance for width would be at a minimum.
