The site is in Danish, but you should be able to easily navigate if you follow these instructions:
You put DVDs in your basket by clicking on the blue basket symbol. Your basket is placed on the left side of your screen ("Kurven").
You go to checkout by clicking on the blue "Til kassen" link:
At Trin 2 you confirm your address. Click on "Næste trin".
At Trin 3 you choose "Betalingskort" to pay by creditcard. Click on "Næste trin".
At Trin 4 you confirm your order by clicking on "Næste trin" and you'll be forwarded to a secure site to key in your cc info.
At Trin 5 you key in your cc info. "Kontrolcifre" is a 3-digit security code used in Denmark and some other countries. If your credit card does not have a security code you leave this field blank. Click on "Betal ..." to finalize the order/payment.