Print out your picture you would like on your onsie.
Trace print onto freezer paper.
Cut out trace with exacto knife to make your stencil.
Iron cut out onto onsie, make sure you ironed the edges well. You don't want paint to bleed!
Paint over stencil.
Let dry. I like to let mine dry over night.
Pull stencil off and you have your print onesie
*(make sure you wash them alone the first time before you wash them normally with your other loads)