If we were going for a still picture, our work up to this point would be enough, but we want Gus to move! The next step is to give him a skeleton, or Armature, which will move him. This is called the fine art of rigging.
This tutorial will show you how to rig eyes for animation in Blender. This is one of many ways out there, this is one of the simplest but one of the most effective by our standards.