Navigate to the tab Login/Register.
When on that page, select “Register as a Student”.
Fill in the details, and then select "Create my account".
Navigate to a course you wish to purchase.
Select 'Take This Course'.
You will be redirected to your cart, where you can either enter a promo code, or just select 'Checkout'.
You will then be redirected to PayPal.
You can either pay with a PayPal account, or simply pay with a card via the button 'Pay with a Card'.
After this has been complete, the course will automatically be added to your account.