One way is to find a performance that you know you won't use and initialize it. Then assign four new sounds of your choosing to the four slots available, and store.
Pull all the sliders down and then raise the one relative to the sound that you want. You can then hear that sound but not the other three. Raise and lower the sliders to access the other three sounds as desired.
You can also split one or more of the four(when editing) and play two together or play any or all as layers by means of using the sliders.
You can also turn three of the sounds off by using "performance control" mute/solo buttons.
That is basically what you do but all of these procedures will be found in detail under performance playing, editing etc. in your manual. All splitting, layering, etc are accomplished in the performance mode. The manual will give you step by step instructions. Hope this helps some.