Yep, what deancorp said also keep in mind sometimes the installer does get a little goofy and doesnt refresh always or right away. I was trying to install community sources from installer and it wouldnt even appear on the list until i refreshed it for about 5 minutes
Sometimes reinstalling installer helps me. Go into installer, the uninstall tab, system, installer and instead of "uninstall" it says "reinstall". Reinstall it and try again.