Username field in contacts list - what is the purpose?

I added a members area to my site and ideally I’d like users to be identified on the site using a unique user/display name. In the contact list (registered members on the site), there is a pre-existing username field. I can go in to each contact and edit this field manually, but why would I want to? How can I give users access this field to populate field? There is no field for this on the Wix members area registration form that I could find. In addition, in the my account page, I can’t find a way for users to edit their display name.

I’m trying to create a website where people can submit anonymous content and have their content listed by the username that submitted it. Does this require deleting the Wix member registration form, setting up a new, separate members database, and creating a custom form even though that field already exists?

Which ‘username’ field are you talking about? Can you share a screenshot?

If you are talking about the ’ name ’ field then you can set it during registration by passing the first name & last name parameters under the contactInfo variable

wixUsers.register(email, password, {
    contactInfo: {
        "firstName": 'James',
        "lastName": 'Bund'
    }
});

Thank you for your response. Please see the screenshot below for the specific field I am referring to.