Be sure you have drive that's big enough to hold all your packages.
Connect External Drive to your computer, Open Casper Admin (6 yes, 7?), drag your drive into left pane (way at the bottom where it says "Local Drive")
Right_Click the drive in the pane, sync it.
I first partitioned my drive w/ a boot volume and put the sync on the other partition, and then I had a free-standing Casper imaging system (and a poor man's offsite backup too!)