The Apple Support Communities are an international user to user technical support forum. As a man from Mexico, Spanish is my native tongue. I do not speak English very well, however, I do write in English with the aid of the Mac OS X spelling and grammar checks. I also live in a culture perhaps very very different from your own. When offering advice in the ASC, my comments are not meant to be anything more than helpful and certainly not to be taken as insults.
You have an Apple ID already, so unfortunately the instructions in this link will not work for you as it states that these instructions are for those users who have not yet created an Apple ID as you may easily read.
If you have not created an Apple ID yet, this article will assist you in doing so on your computer in iTunes or on an iOS device.
If you wish to create another Apple ID for use with free content, my experience with experimenting with the instructions in this Knowledge Base article have always resulted in a None option in literally dozens of different country's iTunes/Mac App stores
Those users with an existing Apple ID are redirected by this article to a different Apple Knowledge Base article which unfortunately will likely not assist you in your goal of downloading Apple content without supplying a bank card or an alternative payment method, such as an iTunes/Mac App Store gift card.
If you have registered your product or used any Apple services, you should follow this article to use an existing Apple ID with the iTunes Store or Mac App Store.
That paragraph, by way of the hyperlink, then directs users with an existing Apple ID to this article;
Following the instructions in this linked article will likely not offer you the None option.