Midi-Shield - signal interpretation

Hi everyone,
we hav the following problem:

we want to write a kind of guitar hero for e-drums. For that we need to interprete the midi-out signal of the drum computer (yamaha dtx-plorer), but we do not know how. The plan is to differentiate between three different pads of the e-drumkit. We're noobs so please be clement :wink:

What preperations do we need to make?

THX