Lay out your plastic sheets on a flat work surface and use a compass cutter to cut perfectly round circles out of the plastic. If you want to have different-sized polka dots on your wall, create a different-sized circle on each sheet to suit your needs.
Clean the walls and make sure they are primed and painted the color you want them to be. The polka dots should be a finishing touch on already-painted walls.
Lay the stencil against the wall where you want to paint a polka dot. Secure the stencil in place with painter’s tape.
Dip a small, foam roller in the paint you want to use for your polka dots and use the roller to fill in the circular hole in the stencil. Apply several coats until the polka dot is completely filled in.
Repeat this process to create polka dots all over the walls. Use the same color throughout or different colors to match the theme of the room. Use a combination of large and small dots, depending on how many stencils you made.
Accessorize the nursery with polka-dot printed items such as blankets, curtains and polka-dotted toys.