You can change the order of your images within your albums on the individual album page.
When in an album, hovering over the thumbnail will show a number of icons including a 'move' tool which will allow you to 'drag and drop' images into the desired order.
You can find more information about managing albums on our blog post here
For photographers subscribed to Picfair Plus, you can find more information how to connect Albums with your Store on our blogpost here