Pull back the Support hand thumbstick and make sure you have the Layers panel selected, the first button on the row of icons at the bottom. From here you can rename, delete and merge your layers. For example you can use the eye icon next to the layer to hide individual layers as you work. If you point your Tool hand at a part and hit the trigger, you will automatically select the relevant layer, indicated by the yellow highlight. To cut a particular layer, reselect the main layer and continue cutting the model into individual parts.