can't find kernel source tree
I'm trying to install the Nvidia driver and I get the following message after I type make install
===> src (install)
"/usr/share/mk/bsd.kmod.mk", line 12: "can't find kernel source tree"
*** Error code 1
Stop in /usr/home/Kalital/NVIDIA-FreeBSD-x86-1.0-8178.
I am not sure of the problem I don't have much experiance with Unix problems.