The Idea in building is to make rooms and connect them so that people can freely travel between them. Creating a room, does not, in itself, connect it to FluxWorld. To have it accessessable by more than the magic of @teleport, it is necessary to link it through the use of the @dig command to create the exits
The next step should always be to make the room interesting. This includes making a description for it (what someone sees as they enter).
The Next steps are usually to add messages to the exits. By default, the system will only respond with: (name) has arrived. - or - (name) has left. but you can be MUCH more creative in saying something like: (name) has wandered out the door and boy will %s be sorry that %s's missing out on all the good conversation.
Those strange looking %s will substitute the word 'he' or 'she' depending on the gender of the person that left. See 'substitutions' and 'pronoun' for more help on this.
That should get you started on building. The rest is practice, creativity, planning, and experience.
Be sure to read up on all of the following commands: @dig, @create, @describe, messages
Also: there are many roomtypes already built, using @dig will only create the simplest type of room, where using @create #173 named Freebles Hangout will give you a room with all the rich features of the rest of the rooms in FluxWorld.