Unable to subscribe to Apple TV

1. Create an Apple ID account, if you don’t have one yet, with full user information as requested. Link a valid payment method to this account (for subscription fees and other purchases through Apple that you may do in the future). For new accounts: verify the email address by responding to a test email message. Users are advised to activate two-factor authentication, which requires adding a “trusted phone number” to the account, on which to receive authentication codes when needed (when signing in on new devices).
2. If you need to edit the account information, at any time, without Apple devices, then please do so in the Apple TV app for Windows, or else on the web at: Manage your Apple ID - Apple.
3. Find the Apple TV app or Apple TV+ app on your smart TV. Open it.
4. Sign in to the Apple TV app through the in-app Settings (sidebar menu on the left), using your Apple ID account.
5. Find Apple TV+ content (easiest through the sidebar menu).
6. You would be prompted to subscribe. Follow the on-screen instructions.

Apple TV app user guide for smart TVs and third party streaming devices - Apple Support

Apple TV app user guide for Windows - Apple Support

You may alternatively start your subscription on any other supported device, including on the web: tv.apple.com.

Get Apple TV+ - Apple Support

How to watch Apple TV+, MLS Season Pass, and more - Apple Support

Watch in a web browser - Apple Support

Do you mean Apple TV+, if so please be MUCH MUCH more specific. Such as what type of device are you using to attempt to subscribe and where are you running into problems?