Step 1: Insert foot into own butt. Step 2: Flight?
(and where’s her other arm?)
Other arm is foreshortened behind her head; you can see her hand behind the wing there. Obviously this does not excuse the piles of anatomical WTF, or the fact that the artist chose to go with an unclear, weird-looking pose. (Or the fact that apparently Tinkerbell is wearing a corset, not a dress, and therefore seriously needs to put on some damn pants because that shit ain’t covering her butt in any situation.