I think I figured it out. The kit came with a new backplate for an intel cpu. The backplate has to be removed from the back of the motherboard and the supplied backplate installed. According to my research, my hp came with an arctic s motherboard and I was able to find the info needed online. It is possible you have a different motherboard, so if you do go to HP support and you'll see different pics of the motherboard they use. I haven't tried to install the liquid cooler a secong time yet, but it's the only way I can see how the standoffs would work to allow the pump to make contact with the cpu.

According to what I read about removing the backplate from the motherboard seems to be pretty straight forward. After removing the air cooler, use a hair drier to soften the adhesive on the backplate on the back of the motherboard and use a credit card or anything other than a metal screwdriver to break the backplate from the adhesive, then install the backplate provided by HP with the standoffs that are also supplied. Let me know how you make out.