Find a small item to do your first practice on like a small wood cut out. You will need your wood cut out, a paintbrush, 2 contrasting paint colors ( light and dark) and your crackle paint. I used Martha Stewart's Brand and get it from Joanne Fabrics for around 8 bucks.
Paint your cut out with your first paint color. I find that using the darker color first works better for me but you can do whatever you prefer. After a quick brush let your items dry completely.
Put a liberal amount of crackle paint on in smooth brush strokes. It is clear like a gel so will be hard to see. the directions remind you to NOT over brush as it is tempting to want to play with it some. Again let the crackle medium dry completely.