Choose an animal that you are going to study. You might be studying hermit crabs, for instance.
Gather items that relate to where that animal lives. In this case, you would gather items associated with the beach. Examples of items include sand, toys for playing in the sand, saltwater, beach chairs, beach towels, surfboards, shells and toys modeled after hermit crabs, and other sea creatures.
Decorate an area of your room to look like the habit. Use the props that you gathered to create an area that preschoolers can enter physically. For example, you might arrange a corner of your room with a sandbox next to a container of saltwater. You could also set up beach towels for the students to lie on and sunglasses for them to wear.
Include an actual example of the animal in a small version of its habitat if possible. This may not be possible for many animals, but in this case, you could easily obtain a hermit crab. Showcase the hermit crab in a terrarium containing sand and water.
Invite your students to explore the created habitat project and to contribute to the project through art work. In this case, you could give your preschoolers coloring sheets of hermit crabs and other beach scenes, which you could display in the habitat area of the room.