If you can, use a thin blade to remove any wood shapes on the front of your shamrock - mine had three wood hearts. It was easy to slide a scraper under them and pop the hearts off gently.
Paint the shamrock with the green paint. Paint the back if desired - let dry completely.
Paint the wood shapes with white paint and let dry.
Paint the wood shapes with Mod Podge and let dry. Paint a second coat and let dry.
Separate the St. Patrick's Day napkin from the sheer white layer. There could be one or two depending on your napkin.
Using three different parts of the napkin, iron the napkin down onto the wood hearts. Place a piece of parchment paper on top of the napkin, and run the craft iron across the top several times (mine was on high heat). While you are doing this, the Mod Podge is melting below the napkin, and the napkin is adhering. Keep going until the napkin is fully adhered, including the edges.
Once the napkins/shapes are cool, use an emery board to gently remove the napkin from the edges by sanding at an angle.
Apply craft glue to the backs of the wood shapes and press them back onto the shamrock. Let dry.
Seal the entire shamrock with Sparkle Mod Podge, including both the napkin and painted areas.
To finish, add a ribbon to the shamrock to hang. Tie several knots on both sides so the wood doesn't slip off the ribbon.