Sculpt on a layer

Select the Layers window.
In the Layers window, ensure the display button is set to Sculpt.
Select a sculpting tool from the Sculpt Tools tray and begin sculpting.
NoteIf Mudbox displays a red warning symbol beside the sculpt layer name, this indicates that the sculpt layer is currently locked. This occurs when the current subdivision level doesn’t match the level the sculpt layer was created on. Use the Page Up or Page Down keys to display the correct subdivision level so you can sculpt on that layer.