First of all check the releases page on github to see if there's a finished release for your platform.
$ cd snifstat-1.0
$ make
On BSD you must use gmake for GNU Make.
$ gmake
$ sudo yum install gcc libpcap-devel
$ sudo apt-get install gcc libpcap0.8-dev libpcap0.8 -y
$ sudo pkg_add -r gmake gcc
FreeBSD 10 by default does not come with sudo.
$ su -
Password: ***
$ pkg install gcc gmake
$ sudo make install
The Makefile is very simple for now so if you need to install somewhere else use INSTALL_PREFIX
in the make args.
$ make INSTALL_PREFIX=$HOME install