What you need
Instructions
This Christmas craft tutorial shows you how to do napkin decoupage onto rocks using Christmas Printed Napkins.
This Christmas Napkin project was contributed by Mandy C F. Thanks for sharing your wonderful photos Mandy!
These rocks can be used table decorations, paper weights or little trinkets. Perfect for gift giving and leaving in parks for people to find and keep. Inexpensive to make so great for group activities.
Paint each rock or stone white
and allow the paint to dry completely. This does not need to be a perfect coat, just a white background because the napkins are quite thin.
Place a coat of mod podge 
or white wood glue 
PVA (dries clear) over the mason jar then immediately place the napkin over the mod podge, taking care to limit the amount of air bubbles or wrinkles in the napkin surface.
Immediately brush a thin coat of mod podge over the surface of the napkin.
Allow this coat of mod podge to dry completely and then coat 1-2 more times.
This looks like a fun project. Just one thing, though. Please reread the instructions because in the 5th paragraph, the instructions reference placing a coat of mod podge on the mason jar. I believe it should be rock.