Turning the heel is the part of sock knitting that scares the most knitters away from ever knitting socks. But the truth is, turning a heel isn't any more difficult than any other part of knitting a sock, you just need to pay a bit of attention.
The instructions for turning a heel typically will say something like:
Row 1: Slip 1, purl 14, purl 2 together, purl 1, turn.
Row 2: Slip 1, knit 4, slip, slip, knit, knit 1, turn.
The first thing you'll notice is that you aren't working all of the stitches all the way across the row. That freaks a lot of people out. But it is the way it must be done.
The process is known as knitting short rows, and it is the key to making a heel that's actually kind of heel shaped.
So step number one is to trust the pattern and do what it says, no matter how crazy it sounds. If we were working a sock with the instructions as noted above, then, we would slip the first stitch, purl 14, purl two together, purl one more and then turn the work like you normally do at the end of a row, leaving the unworked stitches on the needle, as shown.