What is the best way to change password when you forget it on iCloud by

If you could change a forgotten password, that would mean you could change anyone’s password. That would not be a very wise capability for Apple to introduce. Imagine if random folks could simply change your password on any whim.

Of course, you haven’t told us what password you’re referring to. I will guess you mean an Apple ID password. And I will guess it’s your password.

If you forgot your Apple ID password - Apple Support