One of your first stops should be Office de tourisme de Locronan. Here, you'll be able to find your bearings and get some great ideas before you begin exploring.
When you've spent some time at this Locronan tourist information center, why not check out Plage de Sainte-Anne-la-Palud, Plage de Kervel, and Port-Musee? They're not far from Office de tourisme de Locronan and also popular with many tourists.