The company provided details on how to do so in a support document updated today.
Before you change your Apple ID email address, you need to sign out of every Apple service and device that uses your Apple ID. If you want to use your iPhone, iPad, or iPod touch to change your Apple ID, stay signed in to your Apple ID on just that device.
When you change your Apple ID, you can enter another third-party email address or an @icloud.com, @me.com, or @mac.com email address.
Use your iPhone, iPad, or iPod touch
● Go to Settings > [your name] > Name, Phone Numbers, Email.
● Next to Reachable At, tap Edit, then delete your current Apple ID.
● Tap Continue. Enter the Apple ID that you want to use.
● Tap Next.
Use your Apple ID account page
● Go to appleid.apple.com and sign in.
● In the Account section, click Edit.
● Under your Apple ID, click Change Apple ID.
● Enter the Apple ID that you want to use.
● Click Continue.
If you enter a new Apple ID that ends with @icloud.com, @me.com, or @mac.com, you see a message to confirm. When you change your Apple ID to an @icloud.com, @me.com, or @mac.com account, you can't change it back to a third-party email account. Your former Apple ID that ends with a third-party email, becomes an additional email address for your Apple ID account.
More details at the link below...