Since there have been several questions on this, we will add the following instructions to the main page near Rewards-at-a-Glance.
ADD-ON INSTRUCTIONS: To add an add-on to your pledge, follow these steps:
• 1) Press the green ‘Back this Project’ button at the top of the page and select the Reward level you desire.
• 2) If you have already pledged, press the 'Manage Your Pledge' button at the top of the page. If you have not pledged yet, it will say 'Back this Project'.
• 3) Increase your pledge in the 'Pledge Amount' box by the total of the add-ons you want to add.
• 4) After the end of the Kickstarter campaign you will receive a survey that will ask you questions so that you can explain how you would like the add-on money assigned.