Couldn’t sign in my icloud account

See the article If you can't connect or sign in to iCloud - Apple Support

I can’t sign in to my messages on my Apple Watch because the iCloud is out incorrectly. How do I fix this do I needed to take it to the store or can I fix it myself?

[Image Edited by Moderator to Remove Personal Information]

Couldn’t sign in my icloud account on my MacBook Pro