Oly oe thig you have to do : Tap o the butto or use keyboard space bar or us shoulder keys o game pad to take off.

Tap on the button or use keyboard space bar or us shoulder keys on game pad when red pointer comes to the red area of end of line to move the rocket to finish.
Red area of the right end of the bar is the best position to move long and finish the level. if not end of the line (red area) you will have to try again.
Enjoy!