Make sure you are on the shop for your country for correct VAT and shipping calculation. Press the flag in the top-right of your screen and a popup will show the available shops. Select the most appropriate shop for your country.
If you want to purchase a product press the order button for that product and add it to your cart. The cart will be updated and show the number of items in the cart. Press the cart to go the the checkout page. The contents of the cart will be shown:
Press continue to go to the next step. If you are not logged in yet, you will have to do that first. Either you can login into your already existing account, or you can create a new account. If you are logged in, you will be giving the shipping options for your country including prices. Select the preferred shipping option and press continue. Some shipping options may give you additional options, like pickup locations or timeframes.
After selecting a shipping option, you can verify the order and choose a payment option:
If you have any reference for the invoice, you can enter it here as well. Press continue to proceed with the selected payment option. After payment was successful, you will return the site and a green notification is shown. If the payment failed, the notification will be red and offer an option to try again.