When the cookies have cooled down completely put royal icing into a piping bag with a thin tip or a very small hole and decorate the way you like it. It might take a little to get the grip of it, if you've never done that, but you can do it!
Try to use eggs that are fresh and kept in the refrigerator to minimize the risk of bacterial infection.
Keep in mind that royal icing contains uncooked eggs, so be careful not to serve them to pregnant ladies, babies, small children, or other high-risk people.
Recipe by Anja Burgar | Use your Noodles | www.useyournoodles.eu