Add the source to your /etc/sources.list or /etc/sources.list.d/:
deb http://apt.rbel.co/debian/clearskies/wheezy/ ./
Import my GPG key:
sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com F345BE74
Install it:
apt-get update && apt-get install clearskies
Start it:
clearskies start