Once you have built your basket, you will need to scroll down until you see the 'Save Basket' button. This will appear on the right hand side of your screen just above the 'Checkout' button. Simply just press the 'Save Basket' Button.
Once you have pressed 'Save Basket' you will receive a notification across the top of your screen notifying you that your basket has been saved.
You will also then be taken through to your basket screen, where you will be able to see all of your saved baskets.