To decrease their naps, eliminate the nap, but consider putting them to bed 15 to 30 minutes earlier. Once you decide to eliminate a nap, stick with it. Engage your baby in stimulating activities during that time, as opposed to activities that may put them to sleep. Try adding an outside play time during what used to be nap time or play with paint, or toys.
Know that there may be some fussiness involved as your baby adjusts to their new routine, but this shouldn’t last more than one or two weeks.