As I don't have an nForce board I can only guess that after unpacking the drivers you take a look at the files inside and see if there is a readme or install. Failing that there is a Makefile so you can type make.
agpgart: if you don't have kernel support for it use Option "NvAGP" "1" in the device section of your XF86Config(-4). But my system is much faster with NvAGP 2. Your mileage may vary.