Payment is made through Paypal but you don't need to register with paypal if you don't want to and can use your Credit Card. If you already have an account with Paypal already, simply log in.
Once payment is made click on the 'return to merchant' button and the download screen should be shown (see install help). If you are not shown the download page check your e.mail for the order confirmation. This will also have a link to the downloads page. The download link will expire after 24 hours.
NOTE : Please keep your timetables files safe and keep a backup copy incase you have problems or change your PC.