When you open the roOomy Reality app for the first time it says Create New Layout or you can select from some of our templated designs.  

You can then select to create in AR to create a new scene or Open in AR to open a pre-existing layout. 

Go through the interactive menu to find the floor, and start adding or removing furniture. You can modify the location of a furniture by selecting the piece of furniture and using the move or rotate functions. 

You can toggle between AR and VR when you have no furniture selected.