I just downloaded the Quake 3 Game engine, and i don’t know how to use it. i don’t even know how to open it…will somebody please help a NOOB>?
why not posting it on quake forums?
here you’ll find little help
Check out quakeSRC. They can be pretty helpful.
The engine is free, the game content is not. To make it run you will need at least the demo content, better to use the pak file from the full version. Still pretty cool that John Carmack offers the engine as Open Source. Real fans bought the game a long ago anyway. 
What you need to do is moving the pak files to your /base dir, then it will run as supposed.
Maybe you can mix something working from the demo and some mod.