well normally, if your install has gone ok, it should be using the generic nvidia driver (nv).
If you want to use the actual nvidia driver, you have to down load it, then go into init 3 login (all text) and run it, then you make a couple of file changes which actually tell the system the driver to use - the run part of that actually makes the kernel module for it - then if you want to installl a different kernel you have to do it again.
here's the link
to the nvidia drivers page - get the readme file as well, it has pretty good instructions on how to install the driver.
But, before you start trying to install it, open a terminal, and do
that tells you what kernel version you're using and then go into the software manager and you will need to get the kernel-sources for that kernel installed - the nvidia driver wil not install without both the kernel and kernel sources.
Maybe that helps a little
p.s. the file that you'd need to mod is something like /etc/X11/xorg.conf and has a bit that looks like this ------->
# Device configured by xorgconfig:
Identifier "** NVIDIA (generic) [nv]"
# Insert Clocks lines here if appropriate
Where it says "Driver" (without the quotes), yours should just say "nv" with the quotes for the system to work with the generic driver, if it says "nvidia" like my example that's why it won't give you a GUI because you're telling it to use the proper nvidia driver, but you won't have got it installed.