You’ll want to use the ChanServ command:

/chanserv set #YourRoomName secure on

Which will limit the room to only those who have registered their nicknames with NickServ. More information:

Syntax: SET channel SECURE {ON | OFF}

Enables or disables ChanServ’s security features for a

channel. When SECURE is set, only users who have

registered their nicknames with NickServ and IDENTIFY’d

with their password will be given access to the channel

as controlled by the access list.

Hope that helps.