This compression ring is especially made to allow a Cane Creek Forty headset to work with a Jones Truss fork (works with all Cane Creek headsets that have a metal crown race).
Install this ring underneath the regular crown race, and then install the rest of the headset as usual. Check out the instruction in the Jones Truss fork installation guide. The guide is for a Jones H-Set, but the steps are essentially the same:
Start with a 1.5mm headset spacer on the steerer tube, then slide the compression ring onto the steerer. After that, just put the headset together as described in the manual (taking into account how the headset differs fro the Jones H-Set).