First learn to sail backwinded with forward drive and steering control. Understanding the need to keep the windward rail in the water is important to the heli-tack.
Once you do that the heli-tack is a matter of bearing way off while backwinded and then changing places with the sail.
To bear off, pull your back wrist into your back shoulder and extend your front arm. Feel that there is minimum power in the sail. Feel that your front foot and the board are getting swept behind you, ahead of the sail. (The sail is pushing them from upwind.)
When the board is on a broad reach, take a big step back with your front foot, pivoting your back foot on the center line, and landing both feet on the center line. Don't do anything with your arms. Especially, don't push on the clew.
Now you should be sailing clew-first. If you are losing the sail at this point make sure that you are bearing off far enough. If you are still losing the sail then keep in mind that after the sail flip you are clew-first, so you need to PULL on the clew even more if you want to depower. Beginning the whole thing with your clew hand way back will give you more leverage when that moment comes.
After you regain control, flip the sail as in a normal jibe. To me the version where the sail flips right away fosters a bad concept of the move and bad technique, aside from being harder, so save it for after you learn the hang-on version.