Access the users page, from the Configuration / Users Management menu.

To edit an existing user, click on the edit button :

The 'edit page' is the same as the 'add page,' but it comes pre-filled with the user's existing data.

The user name can be changed. It must contain only lowercase or uppercase letters, digits, spaces, or hyphens.

You must fill in all fields.

Once you confirm the updates, you are redirected to the User Management page.