As Vince said, increase throttle to lift heli into air.

Then,
if heli turns left, push rudder stick right... (left hand stick, same as throttle)
if heli slides left, push cyclic stick right... (right hand stick)
whatever the heli does, do the opposite on the sticks to keep it stable...

This all sounds very easy, but the heli will move faster than you can react. No really, it will. It you react directly to what you see then the heli is already moving... by the time your thumbs catch up with your brain and you move the sticks the heli is moving fast. This means you'll push the stick too hard/far and overcompensate, sending the heli off in the other direction.

The skill is in predicting what the heli is going to do and preventing it. This is something you can only learn by doing it.