1. You must rez the beatmaster nearby or none of the drums will work!
2. You must only have one beatmaster rezzed! (Rezzing more than one could be as bad as crossing the streams in Ghostbusters, don't do it!)
Once you rez the beatmaster, just start popping out drums by rezzing or wearing them. You'll hear that the drums play in sync. Not all loops go perfectly together, there are many "feels" represented, but you will find that most actually fit together nicely, a couple are a bit crazy, and a few are pure musicall gold! Experiment with which start slot you use by clicking the beat at different intervals.
The beats are coded across all drums by color names. These names do not necessarily indicate compatible loops, but in the case of you finding something really sweet you can note that, for example, the Djembe was playing Green beat, the Drumset was playing Pink and the Congas were playing Red. You can use this information to recreate your beats.