Step 1: Log in to your account
Step 2: Head to your account page and select the date you placed your order for
Step 3: You'll see an option to edit your order, click it
Step 4: Add or remove the items you'd like
Step 5: Navigate to the basket in the top right, click it, scroll down to the bottom where it says continue and click it
Step 6: Confirm your order and you're all set!