After you have installed your system, you will no doubt want to update your ports tree regularly.
To do this, edit/create a file called /root/bsdports which contains the following:
*default tag=.
*default host=cvsup2.us.freebsd.org
*default prefix=/usr
*default release=cvs delete use-rel-suffix compressports-all
You should change the host “cvsup2.us.freebsd.org” to be one of your local mirrors. You can see a list of mirrors at http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/cvsup.html#CVSUP-MIRRORS
Now to update your ports tree, type:
csup /root/bsdports
This takes quite a while, and will report any files it is updating as it goes. Once it completes, your ports tree will be up to date.
You can also use portsnap(8) tool. It is now part of freebsd base.