You are best off to practice this maneuver on a sim. With a small electric heli like the Belt CP or Blade 400, they are hard to do at anything much over 15 feet up. Basically you need to do the following (from what the sim has taught me):
1. Be in Idle up mode
2. Loose power (by flipping the throttle hold or having your ESC catch fire)
3. Give full negative pitch to the blades as it falls while doing some forward flight
4. about 4 feet from the ground tilt the nose up just a hair and give it positive pitch. This should slow the heli down
5. quickly reduce positive pitch and control the heli landing.

This is not easy to do. I crashed the first 10 attempts in the sim with a larger heli. Larger birds are easier to do this with and it can be done from 100 feet up or more. I have seen a heli stall inverted and the guy was able to right it and land it. If you loose power with an electric heli, something else is wrong.