open konsole session
pkg_add -r libdvdread
pkg_add -r libdvdnav
pkg_add -r libdvdplay
cd /usr/ports/multimedia/libdvdcss && make install distclean
pkg_add -r => fetch package from remote server and install it along with any thing it requires.
Gentoo portage / emerge was based on FreeBSD ports system, read the link that was posted to learn more about the 'make install' thing.
Being at work on a GUI front end for ports, I'll refrain from comment on that issue.