There should really be an easier way to do this from Launchpad. For example, they say:
This repository is signed with B9F2A424372C883C411D917F5AFADBD4AA1C92B0 OpenPGP key. Follow these instructions if you want to install packages from this PPA.
Is there an easy way to just copy and paste that string somewhere in Import under Software Sources and have it work? If not, there should be!

And for record, "Follow these instructions" link is not very helpful. I was able to figure it out, but it's definitely more complicated than it needs to be!