Load your applicator (in this case, an airbrush) with the colour for the stencil and do a test spray onto the masked area to clear the nozzle and check spray intensity and width.
See the section on ‘Medium Application Ideas’ for suggestions on other ways to use your stencils
Lightly spray around the stencil mask in light coats to build up the colour. Too heavy a coat may result in a little bleed beneath the stencil.