It sounds like your home was wired for distributed stereo sound. At the location that all the wires were "home run" to you will need some type of amplifier set up. There are many variations of this depending on how much control you need and how much you want to spend.
If they did not wire in wall volume controls in each room you will probably want a way to control at least that for each room. The most basic set up would be a stereo receiver and speaker impedance matching selector. To add individual volume control an Aton selector can be used:
http/www.atonhome.com/home.html
If they wired cat5 to an wall location you can use a keypad controlled system. Or you can use Sonos
www.sonos.com
If one of your rooms is prewired for surround sound then you will need a surround sound receiver for that room. Many of these have the ability to drive a 2nd zone of stereo speakers so that may work for you in the other rooms too.
If you are not comfortable with your learning curve get a pro in to let you know what you need.