This is how to Airwalk.
Do Ollies of the top and of the sides. It needs to have a pretty steep angle and at least to be 2 or 3 feet of the ground. Once your getting better at it, do Nosegrabs of the side. (it's easier to do Airwalks of the sides than straight off the ramp.)
And then all you have to do is kick your back foot to the heel side of the board, your front foot to the toe side of the board, and afterward the opposite (front foot to the heel side and back foot to the toe side). This should look like you are walking in the air.
Grab it with your front hand and quickly but it back under your feet.
...There you go, pretty simple.