To add items to your shopping cart, first browse or search for the products. Once you have found the product, change the quantity of the item(s) in the product table to the number you wish to purchase. Remember you can always change this quantity later in the shopping cart. Click the "Add to Cart" button at the bottom of the table.
You will then be in your shopping cart. You should see the item(s) you added in the cart, along with any items that were previously added.