You should try to provide a little bit more information, since more than one MUSH/MUX codebase, derivative exists and there may be some differences. What MUSH/MUX codebases do you have/use?
Usually on such systems it's a server setting that allows players to create stuff (either by adjusting a quota for the total number of object a user may create and then own at a time), and some games have a cost to build something in in-game currency. You'd need sufficient currency, sufficient quota, perhaps permissions to use the building commands, and a place to attach the room to (a parent room). The exact commands used to determine if the appropriate configuration is set probably vary in naming, which gets back to the question above. After that it's as simple as owning or having permissions for the room you wish to modify, at least I think so.
If you could explain what you mean 'seeing' or 'not seeing' the rooms that would help. Is it that they cannot get to the room, that there is no description for it or some other issue? Perhaps you could include quoted output from the game, in your forum post, that shows what you are talking about.
I assume you created a room using @dig or a similar command where you give it a name and perhaps a parent room and it makes a new room. Have you made exits that connect the rooms together so a regular player can get from one to another? Can your other player (non-wizard) use a jump (@jump?) or teleport (@teleport?) command to go to a room with a known id? How much do you know about flags or locks and does your server have such features? Limbo is probably the room that 'player_start' or some such variable is pointed at, so any player that logs on (particularly a brand new one) gets dumped there (except wizards or characters with alternate home room?, etc). To get out you need an exit that goes somewhere else or you could probably change that start room to a different dbref# (database reference number).