You get 1 free Snapshot with every BladeVPS PureSSD package with the exception of the X1. For the PureSSD X1, you can order them in the VPS tab in your control panel. A snapshot will literally copy the state of the VPS as the state it is currently in.
Creating a snapshot is done via the Control Panel. Once logged in navigate to the 'VPS' tab and select your VPS. You will find the button 'Snapshot' in the menu on the right. From this menu you can create and use snapshots. You can only create and save one snapshot at a time. Should you wish to create a new snapshot, you will need to delete the old one first (or order an extra snapshot).