How do I set up a new email account

See -> How to create a new Apple ID

How to create a new Apple ID – Apple Support (UK)

See this Apple article: Sign in with your Apple ID

Sign in with your Apple ID - Apple Support

👉 Use one Apple ID to access all Apple services and make all of your devices work together seamlessly. 

You can't merge multiple Apple ID.

See also this Apple article: Change your Apple ID

Change your Apple ID - Apple Support (SG)

Read again -> Related Article ->Add an email account to your iPhone, iPad, or iPod touch

I want to create a new email address for my wife