Do I understand correctly that the coupon gives the right to access all files at once, as soon as you add one of the assets, or do you need to add each asset separately in the provided package? (separately download it so that it appears in the library)
Viewing post in How do I add to my library?
When buying a project, you get access to all the files in it. You don't buy individual files. You can pay more to access certain files that have a special price, if there are any, but you still pay for the project. As a whole. Your library contains projects. Not files. You can't add files to your library.