You will end up with a curved pattern like the one above if your lampshade is bell-shaped like mine.
Cut your pattern out with a pair of scissors.
Wrap your pattern around your lampshade to make sure it fits. If you need to trim it down a bit it is better to do it now than with your actual fabric!
Grab your fabric and place your pattern over top. Using a rotary cutter and mat, cut out your pattern.
I used Jac-Cyn Designs for Birch Fabrics, Mod Basics, Organic in Abacus Pool from my wonderful blog sponsor, Fabricworm.
For the next step you have a choice. Take your spray adhesive and either 1) spray the lampshade or 2) spray the wrong side of your fabric. I tend to spray the lampshade since I find the fabric often sticks to itself if I spray it causing it to wrinkle!
Then ever so carefully cover your lampshade starting at the seam, smoothing out the fabric as you go round. I like to use binder clips or clothespins to help hold it in place while the adhesive dries.