If you need to get rid of polish you already have on, I really recommend the Bourjois 1 second nail remover, it's around a fiver in Superdrug and is one of the best things I've ever bought. It really gets the polish off fast and leaves a red fruit & vanilla fragrance, delish!
First, prepare & protect your nails with a quality base coat. This stops staining & stops your nails ageing
Then paint a white base coat. I usually do two coats, but one might be enough as it is just for the edges.
Carefully paint on your chosen middle colour, I used gray, but brighter colours looks great too! Leave to dry. Add a slick of topcoat - I used a shiny one but a matte top coat gives this look a classy edge - & you're ready to roll!