If your system is an Application Help System, then only admin users are allowed to log into the system, normal users are not allowed login so they do not have username and password.

If your system is a Knowledge Based System, it will connect to Active Directory server in your organization and sync the credentials information automatically. So you can just use your windows username and password to log in. However, in case if you do not know your windows username and password, you can try to use your organization email username and password. For example, if you email address is smith@yourdomain.com, you can use smith as your username try login. If you still cannot log in, the reason maybe your AD group are not allowed to log into the system, so you need contact the administrator for this problem.