how do I edit icloud account information so my name instead of my husbands appear in sent email header

Open address book of Mac , click on the contact that is to be edited and change the first or last name see the picture in the article Update contact information in Contacts on Mac - Apple Support click on edit and remove the first name , enter your name and finally click on done to save .

Open mail application and compose Compose and reply to email messages in Mail on your Mac - Apple Support a mail from iCloud , and send .

When mail header is opened Show detailed headers in Mail on Mac - Apple Support

Your name will appear see the arrow pointing towards the contact name ( its hidden using preview , just an example to explain ).