The accounting of the time and traffic per connection will be implemented in one of the next releases. To add other authentication domains (Kerberos REALMs and RADIUS domains) you have to click on the button [+] in the section [Captive Portal][Authentication][Authorized Domains] of the web GUI. After that, the new added domain will be listed to the users of the captive portal.
The user can select the domain in two manner:
1) by selecting it in the combobox
2) by append it to the username in the form username@domain