If you are an account administrator, you can manage account users by navigating to Account Admin > Users.
On this page you will see a list of the account users separated into two tabs - Active Users and Suspended Users. Suspended Users are users that you may not want to delete, but you also don't want them to have access to your account at the current time.
To add a new user, click the green Add User button on the left hand side of the control panel above the user table. A window will appear for you to populate the new user's details and permissions.
To edit a user, click on their username and a window will appear to update the user details. If you want to change the user password, click on the Change Password tab.
The account owner cannot be deleted, and only the account owner user themselves can edit that user records. Other admin users who are not the account owner cannot change the account owner record.