You have to use the Behringer Synthtribe software utility to connect your computer to the TD-3 over USB, and then you can can set MIDI Channels for Rx/Tx, pitch bend amount, key priority, transpose, multi-trigger and slide modes, clock source, and accent threshold velocity. All those parameters can only be set using the software utility. It also has a pattern editor, which can be quite handy...How?! (via USB).. I could really use some help. you use Ableton?
https://www.behringer.com/downloads.html