We don't really have enough specifics to diagnose the issue properly, but on the surface it sounds like an alignment issue. You seem to be getting unwanted rotation while in the air. A very common problem for early park riders or anyone just starting jumping while free riding is landing on the heel edge with the board at least pertly across the hill. In almost every case, the rider opens up and faces forward once in the air. Any, even slight, twist of the upper body in the air, will rotate the board. So you have to be totally, aligned with your board; hips and shoulders.
Now, if you are not rotating in the air and landing straight, but on edge, this is caused by lean while in the air. If you hunch over even slightly in the air, you will land on the toe edge of the board. Any slight lean back will cause you to land on the heel edge. Its all about eliminating all rotation and staying stacked vertically over your board.
When doing any freestyle maneuver whether in or out of the mark, break it down to ATML:
This standa for Approach, Takeoff, Maneuver and Landing. Right now the two big things you want to focus on is your Approach and Takeoff; if you get these right, the other two pretty much will take care of themselves for simple straight airs! Most important is a stable approach. This means that you get speed and trajectory set early in the approach; long before you hit the kicker. No last minute speed checks or direction changes. You should feel like you are just riding along waiting for the takeoff to happen.
On the takeoff, you need to just really focus on being totally aligned with your board; no hip, shoulder or head rotation at all. Make sure you go off of the ramp totally flat based and completely stacked over your board vertically. This means no bending at the waist or leaning back. Once in the air (Maneuver) all you need to do is stay quiet and don`t lean or rotate ANYTHING and get ready to land.
On the landing, if you have done everything else right, this should be a non event. Just engage the board with the snow and ride away. One big mistake many riders (and all of us once did) is to get spooked by the speed and try to brake check immediately. This can be a horrible thing to do because often, the rider does it before the board has really reengaged with the snow and they loose control in a big way. Allow a second or two to pass, before slamming on the brakes. This time allows you to go from air, to ground riding again.
It takes time to get this all dialed in and you are not going through anything we all did`nt go through. Just keep at it and keep it small until you get it worked out to stay safe....