The "add to basket" button is to be found on every item's information page. Click this to add an item to your basket. Clicking more than once will add multiples of that item to your basket. You can adjust the numbers you would like to buy of any item on the shopping basket page.
A miniature version of the basket is displayed in the top right hand corner of each page. To see your complete basket, click on the "View basket" link in the top right hand corner. This shows what is in your basket, how much each item costs and what the post and packing charges are. You can adjust the quantities of items here.
When you are happy with your order, click the "Proceed to checkout" button. This take you to a secure payment screen, where you will be required to enter your payment details. When you press the payment button on this page, the transaction will take place, and the relevant amount will be debited from your account. Nothing will be taken from your account until this point. At that stage the transaction is complete.