There is a circular walk which will get you most of the way around the island in a single day (approximately 8 hours), allowing you to see the best it has to offer. This is a long (17km) walk so make sure you come prepared!
If you would prefer to learn more about the history and heritage of the island then visiting the Papa Stour Kirk and Norse Stofa are a must. There are information boards available at both, and both can be found on Google Maps by clicking the underlined links in this paragraph. You can also find out more about both of these landmarks on this website.