The way you use a drum machine in a service will depend upon the coordination of the main keyboard player. The drum machine is going to have to be controlled by that person, whether that person is the worship leader or not. Since the lead keyboard player must start and maintain the proper tempos and styles of the songs, it is his or her responsibility to program the drum machine and know where the appropriate patterns are. The main keyboard player will have to have some idea of how drums should be played or how they should sound in order to program the drum machine. With this basic knowledge, the rest can be learned somewhat simply. If all else fails, ask a real drummer to help you create all of the different drum patterns that can accompany the different song styles that you sing.