Click on a part to add it to your beast. To change that part, just click on a different one and it will substitute. You can read a clue about the animals' body parts in the window when you move your cursor over the part. Look there for clues to the proper habitat for your beast. There are parts to build six real animals from both the savannah and woodlands.
Tails are the hardest thing to match.
If you aren't able to build a whole, real beast, try switch ing tails and habitats.