How can I use white nail pencil, & how does it work?

any good not so pricy brands u advise ladies out there?How can I use white nail pencil, %26amp; how does it work?
Sally Hansen has a cheap one and it lasts forever. You can get it at almost any drugstore or WalMart. It's very easy to use, you can either line the tips of your nails yourself or use the stencils that come with it.