To create a 2D doll animation, first you need to prepare your character sprite sheet with all the limbs as separate sprites. See the following screenshot for reference:

You can also use the example project, and go to the Chapter 03 2D and user interface animationRecipe 03 Creating a 2d sprite doll animation with the animation view directory. You can find the Example.unity scene there, with a Warrior character already animated in the scene's Hierarchy. In the Animation directory, you can find a Warrior.png sprite sheet with all the body parts of the character.