Click the red Play Game button in the middle of the bottom of the screen. Then click the red Play button that appears at the bottom of the next screen. You can ascend to the air from the landing pad by holding the up arrow key. Then use the right arrow key to begin flying forward.
The goal of the first level is to rescue the five hostages who are on the ground. You also have to avoid enemy shots. You can fire at the two ground enemies by pressing C. When you see a hostage on the ground, fly down and press the spacebar to drop your ladder. Once they grab it, you can press the spacebar again to pull them into the helicopter.
ARROW KEYS: control helicopter
SPACEBAR: lower the winch / to recoil
Z: drop chaff