Do you still have the Stencil or is it still available? Best to use a Concrete Tile Paint to do the job using the dry brush method of Stencilling.........
If stencil not available use thin acrylic for stencils and make your own by tracing around the design and cutting it out with a craft knife.....
is it already stenciled & you want to cover it up/repaint with new spray paint? or are you asking how to stencil the rock/pattern/look onto the patio using the spray paints?