If you need to add a new user and replace a current one, this article shows you how to achieve that.
You need to delete your current user. That is possible if you are in the "Administrator" role. Go to the "Administrate" section and click on the "Users" tab. Click on the user you wish to delete and then click on the three dots in the top right corner. Proceed by clicking on "Delete user" and confirm by pressing the "YES" button.
You can now invite new user. How to invite new users and what type of user to choose can be found here.