You will need to put the list into a .reg format. What you should do is create a few bans manually, then find those bans in the registry and export them to review the format.
In the WWW Proxy Server you will want to be looking under:
HKEY_LOCAL_MACHINE\SOFTWARE\Qbik Software\WinGate\Services\WWW Proxy server\AccessRights\Recipient*X*\BanFilter