You need to know your domain. College of Dentistry faculty, staff, and students all use iowa. Hospital Dentistry faculty, staff, and residents use domain healthcare.
Enter your username as <domain>\<hawkid> + password. Be sure to use the backslash character "\" between the domain and hawkid - this is usually the key above the Enter key.
If your logon window has a domain field, leave it blank because you already identified your domain in the username field.