1. Print out what you'd like to write. I just Googled 'free chalkboard printables' and used one of those images. I had to blow mine up a bit to get the size right. If this is your first chalk writing experience, a few large words make it easy.
P.S. You can make your own chalkboard surface with chalkboard paint and a picture frame if you don't have a pre-made one! This is a great thrift store project.