Please follow the procedure
FIrst you please change the currency to USD you can see the option in the top right corner on the website..
Then you please add the products to the cart then click on Checkout.
Next step is the most important step.. After entering your details please click on "PAYPAL " check out for payment.
Then you can enter your international credit or debit card.. and finish your order
Any problem you can chat with the online support team..
NOTE :- The reason you cant complete the order is you are not changing the currency to USD and not using Paypal for payment .