It is so simple really. First I stamp the trees some of which are stamped off. I then cut a circle scrap for the moon. I hold that down with one finger then take my sponge and dab it onto the card with the same ink color. Don't overdo it. You can tell when you have enough on the background.
I use this same technique by cutting a "snow" scrap and placre it across the bottom then sponge the top. This can give you the illusion of a night sky against a snowy ground.