In order to change the enable 2FA on your Xbox Account, you will need to follow these steps:

1. Go to your Microsoft Account's settings.
2. Go to the "Security" section.
3. Click on the "Two-step verification" button at the top.
4. Verify yourself using the code sent to your mailbox.
3. Select "Turn on" and then pick your preferred 2FA method (app/phone/secondary email).
4. Follow the on-screen instructions and provide the code you received.