1. pick up the phone.
2. "I need a new PC, config as follows: <config> "
3. wait till PC arrives & hope whomever build it already had figured out the OPs title question :)

THAT'S WHAT i DO! :P

What type of paste is it? What type of CPU?

It depends on the brand/type. For some pastes a rice grain size line is preferred, for others a circular green bean size blob. I really advice you read the instructions that come with your particular paste.

Just a note though: Doing 1. with a bare finger is definitely not ideal. Your finger is oily. Wear vinyl or similar gloves.

I usually do 5, but a smaller 5mm line, mainly because that's what the instructions that came with the paste said (it's a ceramic type, forgot the brand).

There was actually a research about this somewhere on internets!

The outcome is (if I am remembering correctly):

1) if the chip is protected by heatspreader - apply a small drop of paste right in the middle
2) if the chip is exposed/naked/no heatspreader - cover the top of the chip with thin layer of paste


Edit:
Yes, it was correct. The links: (1/heatspreader), (2/noheatspreader)

Pre-built systems often do a pretty shit job of correctly applying thermal paste. This is especially true if they use the stock coolers provided with the CPUs, which generally come with a massive blob of thermal paste already attached (way too much, and not of particularly good quality).

the video link here is awesome, should have a check, i've already seen, very useful, i would apply a small dot and push heatstink to spread it as it would cover the extreme tiny gaps between the metal while it spreads out, i haven't done this before aswell, i think this would be best

Thats why I order specific configs from IT experts & pay up the difference in component quality & the building fee. That also includes CPU cooling. I'm a total coward if it comes to building 1k worth of hardware together, not a moron (most of the times ;) ).

Not always a great idea. I've seen PCs built without thermal paste at all.

The CPU is AMD Athlon 64 X2 4850e and according to the Arctic Silver's document that was recommended above the cores should be in the middle and they recommend the middle dot method.
The paste came with nothing really because it was from a friend - Noctua NT-H1, from its website I've saw its non-conductive so the worst won't happen.
Since the paste was used and its below 50% now, I will probably won't have enough for "tinting" as recommended by arctic silver (although it looks good practise for pre-filling cavities on the surfaces, but at the same time it might introduce irregularities as with the finger method shown in the tek syndicate's video linked above). The both docs recommend heatsink twisting for even more spread than with only pressuring it, but I'm not sure if my motherboard rail will give me that option.
So probably it all comes to the food again :) - rice or pea quantity of the paste, its probably important to note that my heatsink and fan are from the boxed version of Sempron 3000+.
I've known of "IT expert" that doesn't care at all about client machines and the real ones that care and give iron grade warranty (like OriginPC) the difference in price is quite considerable.
Besides my case is 2nd hand components, so there is no option for pre-building or warranty of any kind + I want to learn how to do it myself :)

Are you saying I should use a steak-size puddle of cooling paste on my CPU?

I put a small dab, about equal to a pea, in the center of the heatsink then press it firmly to the processor. I use similar compound on IGBTs and heat sinks for my work and it works GREAT. If you have excess, dab it with a soft, dry cloth. The paste is non-conductive, but you don't want it sitting around all over everything in there.

Like the manufacturer intended :D:D

https://www.youtube.com/watch?v=kSCVahyh3Dk

No, but actually just put some on a razorblade and use it to put a very very teeny tiny layer on it.

Go with the "pea sized drop" / tiny dot in the middle of the CPU, then push down lightly on the heat sink. As you push, it spreads out perfectly beneath the heat sink and gives the best coverage.

Don't spread the stuff with a card like you're frosting a cake, you're just likely to muck it up and have it ooze out the sides (which you certainly DON'T want).

[]b]Oh, and if you're reapplying, clean up the old dried up stuff that remained from the first application.

A small amount of rubbing alcohol on one of those soft rags used to clean sunglasses works wonders and doesn't take much effort.

And don't "unseat" the CPU to do any of this. If you have an older CPU, you don't want to break one of the flimsy pins connecting it to your motherboard.

I actually did this just recently (I removed my heatsink for a thorough dusting) and realized the original system manufacturer must have done a terrible job of applying paste. As soon as I had my new application on, I was getting cooler temps than the first day I had started using my system!

Who wouldn't?