On izneo’s website:
In order to buy an album, you will first need to either create an account or log in. Once you are logged in, add the album(s) of your choice to your cart and then click on the cart button at the top right-hand corner of the screen. Provide your payment information (more information in Payment Methods). Once you have successfully followed these steps, you will have access to your album(s).

Via the applications: 
In order to buy an album, you will first need to either create an account or log in. Once you are logged in, go to the page of the album you would like to buy and click on “Buy album.” If you have already provided your information via your Apple or Google account, the purchase will be immediate. Otherwise, you will need to enter your bank card information in your mobile phone or tablet.