You can throw them or pick them out of the bag and set them up like you would a tarot spread. I prefer casting them out on a blanket on the floor, but when you're in a situation where throwing a bunch of staves/rocks on the ground is not exceptable, I like to draw one to three from the bag.
If you plan to use the drawing method, get a larger bag for the stone runes. I like wine bottle cloth gift bags . You can find them in a variety of colors and very nice fabric. I've also heard of people using the sachets that come with some brandy and whiskey. If you know someone who has a bar in their home, you may want to ask them if they have some laying around.