Sock pattern BIG help

Ok, so the pattern says the following (it is a sock pattern on 4 DPNs, I already did the cuff and the leg; I am beginning the heel):

" Begin the heel according to the basic rules of knitting socks, doing the decreases on each 3rd row.

Basic knitting sock rules:
Step 1, Heel, upper part: Knit the sts on stockinette st on needles 1 and 4, leaving the other sts from needles 2 and 3 on hold. Knit as many rows as sts you have on the active needles.

Step 2, Heel, lower part: Knit on the central sts of the upper part of the heel or on the central third of the upper part of the heel on stockinette st as follows:

  • Knit the last st of the lower part of the heel with the next st, twisting the sts, turn, slip 1 st purlwise, purl the next st of the lower part of the heel, purl the last st of the lower part with the next st, turn, slip 1 st, knit the next st of the lower part, repeat continuously from * untill there are only the sts of the lower part. "

Then it mentions how to pick up sts and toe decreases.
SOO: What does it mean when the pattern says “doing the decreases on each 3rd row”? And which are the “sts of the upper part of the heel or the central third of the upper part of the heel”? I apologize if some things are confusing, I translated it from Spanish…

I have never heard a heel described quite like that. I think I know what they are talking about, but it is confusing.

Read through this tutorial http://www.cometosilver.com/socks/SockClass_Start.htm
Particularly the heel flap and turn, it’s very clear and should work with what you are currently doing.