It's simple, under Products section, just click the products you want to order and add the item into a shopping cart.  You can then go back and add other items or just click on the Pay & Finish button to complete your purchase. You will then be prompted to enter the Secure Mode (SSL) or Non-Secure Mode to collect the billing, shipping and credit card information.  You will also be given an Order Number (ie:133-14-5993) which is used as a reference.