Getting started with BSDstats on FreeBSD is easy, thanks to the port /usr/ports/sysutils/bsdstats. The port drops the 300.statistics script into your /usr/local/etc/periodic/monthly directory, where the periodic(8) system will find it and execute it in due course. The port also adds the necessary variables to your /etc/periodic.conf.
To set up statistics reporting on your FreeBSD system:
Make sure your ports tree is up to date, using your favourite updating tool such as cvsup(1) or portsnap(8)
Install the port. The port installation script will prompt you for options such as whether you want it to edit your /etc/periodic.conf to enable the script and offer to run the reporting immediately after its infrastructure has been set up.
Once the script is properly included in the periodic(8) system infrastructure, it will be executed at the proper one-month interval. You may want to upgrade the script to newer versions occasionally, just like you would other installed ports.