In order to slice for Palette+, you'll need to import up to 4 separate STL files and combine them in your slicer (We also have a video tutorial on how to slice with Simplify3D and Cura). If you already have a pre-made single body STL model, this may cause some issues as you wouldn't want to re-model each part into their own STL file. This is where MeshMixer comes in.
Below is a video tutorial which helps explain how to separate single color STL models in multi-color/multi-material models with MeshMixer. These multi-body STLs are then ready to be sliced and printed with your Palette!
You can find the video here.