To select an Add-On to go with your pledge, increase your Pledge amount by the amount indicated for the Add-On. At the end of the campaign, a poll will be sent out to confirm your rewards and Add-Ons. There is no additional shipping cost for Add-Ons to your original Pledge.
For example: If your are a BASIC (U.S.) backer, your pledge is $30. If you want to also select Add-On Expansion Tile Set 1 +$10, then increase your pledge to $40.