Press the green flag twice otherwise it might not work. Use your arm to pop the bubbles. Be careful, because the red bubbles will make you lose health, but the green bubbles will give you more health. Minion Bubbles will sometimes appear, and if you pop them a minion appears and pops the green bubbles for you. But look out, because when you get to 300 bubbles popped, a Boss Bubble will appear! He will shoot out bubbles that if they touch the bottom you lose 20 health. Try and beat the boss!
