From a desktop or tablet:
Log into your website account via 'My Account' at the top right-hand side of any web page.
From a mobile device:
Log into your account by click on the 'Menu' button and scroll down to the 'Login' option.
You may have made a purchase using "Guest Checkout" meaning you don't yet have an account. If this is the case then click 'New Customer' and sign up using the email you used for your previous purchase.