If you plan on completing all of the tutorials you will find that there is one that requires you to do this but if not, here goes.
You will need to do this when creating your own level. Just go to the right hand side from the main menu of the pod to "My Moon - My Levels" and create a new level. From here you will need to open the popit and add the relevant items (2 wheels/legs, 2 eyes and a brain) from your tools bag to an object to make it into a living creature. They are all in the creature items section and you can simply add them all to a block of material.