How to Edit MIDI Drum Sound - Alesis DM5

I have an Alesis DM5 drum module triggering from a Pintech drum set. After using the DM5 directly, I finally hooked it up to my PowerBook via an iControl to access the drum kits.

Worked great...mostly. Of my 13 triggers, ten work perfectly. Three, however, trigger sounds I don't want - a conga, a bell and a...blank.

How would I go about reassigning voices to these triggers? I'm (obviously) clueless on MIDI and all I want is to sit down and play. Any input would help - thanks!