I'm a beginner of blender. I have a human model, and my goal is to let the model make expressions, so I have to make its mouth and eyes open. However, the model is totally closed, just like in the first two pictures. I want to achieve the result in the third and fourth picture, where as you can see there are new edges added in the eyes and the mouth.
I want to know what procedures should I do to achieve my goal. Thanks for your help!