First of all, thank you kindly for your support. Just hit the "Manage My Pledge" and include the cost of the second item (or third and fourth). Then message us via Kickstarter (the CONTACT ME link on the right side of the page) and name still available items you are paying for. There is a small chance someone will buy them outright before we get to your message but we are working tirelessly to get you the amazing Fantagraphics books and swag you desire.
Don't see the answer to your question? Ask the project creator directly.