Before you start, you will want to add some protection to your work surface. I used a trash bag to cover my table. And you may want to use gloves if you don't want your fingers stained.
Pour some ink to the acrylic plate (it comes with the roller applicator) and get your roller nice and juicy. Add the stamp you wish to use to the block. I centered it and made sure it was straight to help with the spacing, etc..
You may also want to add some cardboard to the inside of the pillowcase so that you have a flat surface when stamping. My pillowcase has a zipper on the back, so to avoid the lines showing through, add that extra layer of protection.