Assuming you entered from the right, you will two large monkeys bouncing your way. Eliminate them and then proceed to the left. Drop down to the ledge on the left, and destroy another monkey. At this point, you must crouch down and crawl through the gap in order to drop down to the screen below.
As you fall to the middle screen, two other large monkeys will fall with you. At this point, it is still possible to return to the screen above, but only by using Micro-Power and a Jet Pack. However, if you crouch down and fall through the next gap, it will not be possible to return to this screen, even with a Jet Pack, as the game will not allow it.
On the bottom level, walk to the left and eliminate any more large bouncing monkeys that you encounter before reaching the left exit.
