The Superbell flower is actually a hybrid form of the Calibrachoa flower. It is highly prized for its small petunia-like flowers and for its ability to blossom without the deadheading normally required for petunias. Since it is a hybrid, any seeds that form will not produce Superbell flowers but will produce a form of the Caibrachao flowers.
Watch the flowers for any swelling at the base. These should develop into seed pods if the flower was pollinated. Pick the seed pod after it is browned and dry but before it splits open.
Place a container under the seed pod, and snip the dried pod with a pair of scissors so it falls into the container. The seeds are very tiny and easily will blow away, so collect them carefully. The Superbells do not produce very many seeds, so you might have to look awhile to find them.
Bring the collected seed pods indoors and pour them onto a piece of paper. Crush the seed pods between your fingers to remove the little black seeds. Clean out the large pieces of debris.
Fold the paper in half carefully, without spilling the seeds. Pour the seeds into the small recloseable bag, tapping the paper to move all the seeds down. Close the bag, and store the seeds in a cool and dark place until the next growing season.