How do I create a new iCloud email address on iPhone SE?

If you already have an Apple Account and an @iCloud.com email address, but want another one, follow the steps below:

Create an email alias

1. Go to icloud.com/mail, then sign in to your Apple Account (if necessary).
2. Tap  at the top of the Mailboxes list, then choose Settings.
3. In Account settings, tap Add Alias.
4. Provide the requested information:

• • Alias Address: The text you provide becomes the email address (alias@icloud.com). An alias must contain between 3 and 20 characters.
  • Label: Aliases are listed alphabetically by label.
  • Full Name: The name you provide appears in the From field of the emails you send.

1. Tap Create.

See Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support

If you already have an Apple Account but not an @iCloud.com email address, follow the steps below:

Create a primary iCloud Mail address on your iPhone or iPad

1. On your iPhone or iPad, go to Settings > [your name] > iCloud.
2. Tap iCloud Mail (or Mail), then follow the onscreen instructions.
3. If you don’t see onscreen instructions after turning on iCloud Mail on your iPhone or iPad, you already have a primary iCloud email address.

See Create a primary email address for iCloud Mail - Apple Support

Otherwise, follow the steps below:

Create your Apple Account using the App Store on your device

1. Open the App Store and tap the My Account button.
2. Tap Create New Apple Account. If you don’t see this option, make sure that you’re signed out of iCloud.
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5. Follow the onscreen steps to provide an email address, create a strong password, and set your country or region. The email address that you provide will be used to sign in to your new Apple Account.*
6. Enter your payment method and billing information, then tap Next. You can also choose None. You won’t be charged until you make a purchase. 
7. Confirm your phone number. This can help to verify your identity and recover your account if needed. Tap Next.
8. Check your email for a verification email from Apple and verify your email address.

See How to create a new Apple Account - Apple Support