Verify your order and click on Secure Checkout. You will be redirected to the online payment processor where you have to enter your information to finalize the order.
There is no physical delivery, you will receive an email with your license key, download link and installation instructions. Please check your spam folder too if you don't receive the email.
The invoice will arrive in a separate email (as download link or attachment).
The payment process is secure and you will receive an electronic invoice (by email) from them.