To set up free shipping, all you need to do is set up a custom shipping option called free shipping. Then you have the option of setting this rule by weight or by price. If by price, make sure to check that box in the free shipping method, otherwise it defaults to be by weight. Make sure to not check uses rules, and then click on the edit weights button (or edit prices if you are using prices).
From there just set your table up for free shipping. One way that people usually do this is for over a dollar amount. So lets say you are offering free shipping over $100. Then you would set your low price to 100, and high to be 9999999 and then set the price to 0.
Hope this helps!