Don't practice on a single piece of fabric - make a sandwich of your fabric, batting and backing. I used a solid fabric on the top and a different solid for the backing. Then use one color of thread in the bobbin and a different color thread on the machine. And don't make either color thread the color of your solid fabric. This will allow you to see what you're doing and how your tension is. After that it is just
practice. You'll do fine - just don't give up!