Here are the commands that you need to run.
http://www.ubuntulinux.nl/source-o-matic
gpg --keyserver subkeys.pgp.net --recv KEY
gpg --export --armor KEY | sudo apt-key add -
Where is says KEY in upper case letters. You need to place the GPG key there. So you need to run both commands for each GPG key.
Example:
gpg --keyserver subkeys.pgp.net --recv 010908312D230C5F
gpg --export --armor 010908312D230C5F | sudo apt-key add -