Flipping the puck up in the air is pretty simple, but it takes a little bit of practice. As you're handling the puck, you can do a quick toe drag to pull the puck back towards you and in one motion catch the puck on the middle or heel of the blade and then lift it with an upward, forward motion. As you're cradling the puck, angle your blade back so that you can use your blade to scoop up the puck.
Toe dragging the puck before you flip it up from the mid or heel of the blade will help you slide your blade under the puck more easily because of the opposing momentum. You don't necessarily have to toe drag the puck though. You can instead just pull the puck back to you with the backhand of the blade and then catch it on your forehand before flipping it up. Once you get the hang of it, you'll be able to flip the puck up much more easily and you should be able to do it without dragging the puck back first.