Multi-timbral instruments receive MIDI on multiple MIDI channels, each MIDI channel triggering a different part/sound in the instrument.
Multi-output instruments let you route the audio output of different sounds to different audio outputs, which let you process the audio individually (eg, putting a reverb only on the snare channel, etc).
Giving that you now know how to set up multiple audio outputs from your instrument, you know sem to want to know how to configure multiple tracks feeding different MIDI channels (nothing to do with audio).
In Logic, hit the create new track button, select software instrument and check "multi-timbral", and choose how many parts (MIDI channels) you want - probably 8, I'd guess (I'm not a Battery user).
Instantiate Battery and you have individual tracks sending to each MIDI channel.