Bandcrash is just producing files to be uploaded anywhere. If your web hosting allows password protecting a directory (via .htaccess or whatever), that’s all you’d need to configure and everything should work. If that’s not enough information then please share what your web hosting situation is and maybe I can provide more information.
As far as “asset pack” that’s down to how you set up the itch project. Make sure you’ve set your project type to “soundtrack.” You can also provide your own custom noun on the project page. You might also want to enable the “auto-play” option so that the run prompt doesn’t appear.