how to install the nvidia driver (gtx660) in Linux, so that i can use 2 monitors.

warning log

Using: nvidia-installer ncurses user interface
-> License accepted.
-> Installing NVIDIA driver version 340.32.
ERROR: The Nouveau kernel driver is currently in use by your system. This driver is incompatible with the NVIDIA driver, and must be disabled before proceeding. Please consult the NVIDIA driver README and your Linux distributions documentation for details on how to correctly disable the Nouveau kernel driver.
WARNING: One or more modprobe configuration files to disable Nouveau are already present at: /etc/modprobe.d/nvidia-installer-disable-nouveau.conf. Please be sure you have rebooted your system since these files were written. If you have rebooted, then Nouveau may be enabled for other reasons, such as being included in the system initial ramdisk or in your X configuration file. Please consult the NVIDIA driver README and your Linux distributions documentation for details on how to correctly disable the Nouveau kernel driver.
ERROR: Installation has failed. Please see the file /var/log/nvidia-installer.log for details. You may find suggestions on fixing installation problems in the README available on the Linux driver download page at http://www.nvidia.com.