How do you hook a PA system up?

The main outputs of the mixer (L & R) go into the equalizer (L & R) then the outputs of the EQ go into the inputs of the power amps. If you are not using monitors, then I guess one power amp is then sent to each speaker (which is overkill- you should probably use only one of the power amps and connect the speakers to the L & R). The amps may be set to "Bridged" instead of stereo, but that's a whole other subject. Compressors are usually connected to the "inserts" on the mixer channels for vocals, but you could connect them between the EQ unit and the power amp. There's a good manual called "The Sound Reinforcement Handbook" that you can get at Guitar Center or Musicians Friend or the other online music sites.