1. Add watermark (Click the (i) button on the right.)
2. Turn on the right click protection.
3. Add legal disclaimer in the footer or in a popup window.
4. Do not include the high-res or original photos in the album.
Please note, there's no such thing as absolute protection for images on the web. Visitors can easily take a screenshot for example - you can't stop them. Using reasonably small images and adding a watermark is usually sufficient to deter people from stealing your photos.