They accept Visa and Mastercard. You can also pay with Paypal. But at the BI Store you can only purchase digital copies, not physical discs.
Purchase works like this:
You create an account there and log in.
Select the games you want to purchase and drop them in the cart.
Checkout and select what payment method you want to use.
Once paid you get an email with the purchase recipt - save it! and the download location.
Then you download the game, activate it and play.
You can save the downloaded installation files on DVD, Bluray or internal/external HD from where you can install the game at any time you want.
Sending money from Canada to the Czech Republic is nothing I really recommend though. Chances are great the money never arrives.