Your robot is poised to walk, however, you first have to get a leg off the ground. Of course, that is easy enough; if you simply lift the leg by changing the angle of the knee joint, your leg can get off the ground. You may also want to change the angle of the front to back ankle; this will allow you to lift the leg without raising it quite as high.

However, you'll have a problem if you change just these two servos; as you lift the leg, your robot will fall over. This is due to a simple principle called the center of gravity. When your robot is at rest, your center of gravity looks like this:

It is clear that if you lift a leg, the robot will fall over in the direction of the leg that has been lifted. What you need to do is to shift the center of gravity over the leg that will be left on the ground using the ankle servo that can tilt the robot left and right, so that it ends up like this:

You'll then want to set your servos to lift the left leg. Here is a side view of...