How do I add an ICloud account?
How do I add a iCloud account on my iPhone?
iPhone 8, iOS 15
See -> How to create a new Apple ID
How to create a new Apple ID – Apple Support (UK)
FYI: You are sign in here . . . with your Apple ID.
Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.
You can’t merge multiple Apple ID accounts.