Cut the blooms from the stems of the artificial flowers. Remove excess greenery such as leaves. Get down to the basic flower and make sure the center is out so there is a visible hole. There may be two or more layers to the flower -- often artificial flowers are made up of multiple pieces. Use as few or as many pieces as accomplish your desired look.
Lay the string lights flat on a work surface.
Pull out each lightbulb, and fit an artificial flower over the bulb's base. If the hole is too small, stretch the flower material until it fits over the base or use scissors to enlarge the hole. If the hole is too large, keep the flower in place with a small amount of hot glue.
Replace the lightbulbs, making sure the bulb connects directly with the base.