In Performance mode you can setup any four Voices. From the main PERFORM screen press the F3 button (VOICE). This will show you the Voices and how they are arranged on the keyboard (note limits). You can Delete or Add Voices here.

Take a look at the Performance called Hop it for example. When you press F3 you can see how the sounds are mapped. F6 from the main Performance screen shows you how the arpeggiator is assigned to the drums.