The same way you would do a building or house. Draw a floor with posts and put a roof over it. I am not sure what you are asking, but find the educational reseller for your school and ask them to arrange training, find a local user group to attend their meeting, try doing the Revit HELP tutorials, get one of the many books published on using Revit. Your question is a little to broad to answer here without more info and some images/pictures of what you are trying to create.
Mel Persin, aia