Yamaha DTXpress/DTXplorer/DTXtreme

im new to electronic drumming...have used acoustic all the time. i 
just got hold of dtxpress ii...i want to add more pads/cymbals so i 
can recreate my acoustic set. im totally clueless on how to proceed. 
can anyone point me to the light (lol). ive browsed the groups but 
its confusing. thanks