To buy download credits with bitcoin is a quite simple process, if you have bitcoin and know how to use them. With bitcoin you can purchase download credits from two places.
From My Account page
Choose the My Account option from menu at the top of each page. https://hanna-world.net/home/my-account/
Follow the option to Buy Download Credits
Follow the link to the shopping cart
Buy the credits with bitcoins using the Proceed to Checkout option from the shopping cart.
From A shopping Cart
On any shopping cart there is a Buy More Credits option. But be careful, you can not have any other items in your basket if you want to buy download credits with bitcoin.