Removing a package or a port
To remove a package or port, first you need to find the name of the package. For instance if you want to remove kopete, to find out its full name, you will type:
# pkg_info | grep kopete kdenetwork-kopete-0.11_1 KDE multi-protocol instant messenger (IM)
Then to uninstall the package, type as root:
# pkg_delete kdenetwork-kopete-0.11_1
If you installed from the ports, you can also uninstall going to the specific port directory and you can uninstall from there:
# cd /usr/ports/net-im/kopete # make deinstall
To learn more about ports and packages, feel free to read the excellent FreeBSD handbook.