Carbon likes to form straight chains, but sometimes it also forms cyclic structures. In this example, you will create a cyclic molecule and learn to create bonds between atoms in the 3D editor. Let's create cyclobutane. Remember that butane is 4 carbons in a chain, well cyclobutane is 4 carbons in a ring.
You could simply select the cyclobutane button under the ring structure menu, but that would be cheating. Let's learn to create bonds...you'll need it later.