if the stickers are vinyl, then the sheet they are attached to also has a slight amount of adhesive. You stick the entire sheet where you want it, then peel off the backing. (actually attached to the front of the decal)
A few easy ways to do this...
use masking tape to line up the decal sheet
When applying, peel offa little backing at first and make sure the decal stays lined up.
When you finally peel off the remaining backing paper, don't lay it down, but instead hold it away from the surface and use your hand or a squeegee to work the decal into place little by little. This will eliminate air bubbles or creases.
Once the decal is in place, go over where the decal is making sure to press it into place, then carefully peel off the backing.