The next step is to create a new layer for the stairs.
As with previous steps where new layers were added, the same process must be followed to create a layer for the Stairs.
First, open the sidebar.
Second, lock the Fireplace layer since no additional changes have to be made.
Fourth, as before, double click on the created layer (Layer 6) to rename it to Stairs.
Lastly, make certain the Stairs layer is selected and then dismiss the Layers Panel by clicking outside of it.
The Layers Panel will appear as shown below once these steps have been completed.