How can I submit my app if I didn't enrolled for the Apple Developer Program?
The only way for you to distribute your app via the iOS App Store is to have it submitted by someone (or an organisation) that is enrolled with the Apple Developer Program. That someone doesn't necessarily have to be you, but based on your question that seems to be the best option.

You can refer to the Enrollment page to get started, or skip straight to the Start your enrollment page.

If you're getting the Sorry, you can’t enroll at this time message, you should also get a description below that as to why you can't enroll. If you don't, or the message doesn't make sense to you, then you can contact Apple Developer Program Support via this form.