Scrap the paste off staring from the edge working towards the center on both the cpu and heatsink. Make sure they are clean. I just use a kleenex. soft enough to not damage anything, big enough to do the job.

Then unclip your cpu and with your finger press down and make sure it is seated right and re clip it down.

Then add a small dollop of paste in the center of the cpu and using a matchbook cover cut at half width or something simular and spread the paste. Don't go over the edges.Stop just before them. You only need it on the cpu or the sinkheat not both. Cpu is better because the heat sink is quite often bigger than the cpu.

Then clamp the heat sink down and they can be a pain to clamp but it has to be done. Rememeber you only want a very thin layer. The thinner the better.

As for 6 cores. Most everything I use takes advantage of as many cores as I can throw at them. Vue, Modo, Poser, Carrara, video editing, etc. Makes me wonder if the sales person is a gamer as I don't think they take advantage of multicores like our cgi does. 99% of the sales people I have delt with are gamers and don't know much about cgi.