does anyone know how to take a styrofoam castle and cover it with edible glitter to make it like a sand castle like in the bakery craft book?

You can buy premade castles from Cal-Java and cover them with glitter. If you want to make one yourself, you would do it just like you would it you were making one from gingerbread. Cut all the pieces from styro and use royal icing to glue them together. I would probably use a very light coating of piping gel to cover the castle to which the glitter will then stick.