You will want to complete your Apple ID account will full user details as asked, with a set country, a verified email address (respond to test message), and a valid pre-authorized payment method that supports automatic and periodical charges (as that is how subscriptions work).
How to create a new Apple ID - Apple Support
You way want to manage your Apple ID account in the iTunes application for Windows, if you don’t have Apple devices. The iTunes application may show you which account information is missing or incomplete, or needs editing.
Apple ID support - Official Apple Support
Manage your Apple ID on the web - Apple