To break the light bulb, hold onto the toilet paper roll and hit the light bulb end of the maraca on a hard surface. You want to hit it as lightly as possible to get it to break. The main goal is to break the light bulb without smashing the paper mache. The broken pieces trapped inside the paper mache is what will make the rattle noise when you shake your maraca.
Once your light bulb breaks, inspect your paper mache. It is not uncommon for the paper mache to get a crack or two. These cracks can be covered by a few more layers of paper mache or, if they are very small, with a few strategically places pieces of masking tape.