Make sure that your surface is clean and smooth.
The quotes have a transfer tape (looks and feels a lot like white masking tape) on one side, and backing paper (white and shiny) on the other. The transfer tape, which is sticky and transparent, allows you to lift the vinyl letters off of their backing and transfer them to your wall. Before peeling the back paper off, rub the surface of transfer tape to insure the quote is adhered solidly to the transfer tape with a flexible plastic card (something similar to a credit card).
The easiest way to ensure that your quotes are straight on your wall is to use a ruler to make a guideline and then line up your lettering and tape the top edge of it along the guide line (you will tape the lettering to the wall with the backing and transfer tape intact). The tape itself acts as a hinge so that you can flip the lettering up and peel away the backing.
After flipping up the vinyl and carefully peel the backing paper away from the quote, You quote should remain on the transfer tape. The quotes can not be repositioned, so be careful to line it up. Once down rub the lettering again with the flexible plastic object so that the adhesive on the back of the letters themselves stick to the wall. Peel the transfer tape off of the letters and enjoy your finished product!