Well, there should be instructions in the kit on what to do?
With ALL the kits that I installed (HD, Ness, others), you remove the shock adjuster "bolt". You actually need a press, you have to press "down" on the bolt, and remove the ring that goes around holding the shock together. There's a lock nut inside the top, releasing that allows removing the bolt. The stock HD bolt has no adjustment for length.
The replacement is either a fixed (longer) length, or is adjustable, but basically goes back together the same way.
But if you don't have instructions, you're gonna have a tough time with this job.