How do I reset an apple.icloud email password?

Your iCloud password, including the email, is your Apple ID password. (Or, in the event you have more than one Apple ID, the one you used to set up iCloud). So you can change the password at https://appleid.apple.com

https://support.apple.com/HT201355

If your reason for doing this is that you have forgotten the password, please see

https://support.apple.com/HT201487

For the Apple ID password, enter the Apple (iCloud) ID and click Forgot Password. See if you can get an email option if necessary.

Apple ID - Manage            

Apple ID – Forgot Password