This page explains how a proprietary driver for an Nvidia graphics card is installed and configured on (Slackware) Linux.

lspci -v | grep -A6 VGA shows your card type. If 'Nvidia' doesn't appear, you can stop reading now

Go to Nvidia driver download page, select your card type and download the driver.

Create and config an xorg.conf file. See x-server_configuration_old_way

Further edit xorg.conf according to Additional information → README on the Nvidia driver download page.

See also http://www.nvidia.com/object/unix.html