Click on one of the walls and select "Build on this Lot" or "Buy on this Lot". Then take the hand tool and move the sculpture from the sculpting platform to the location on the lot you want to place the sculpture.
I'm doing this now with one of my sculpture sims to build an ice palace bar.
I wanted her to be able to do Sim Ice Sculptures; but, that option is not available on the community lot. Bummer.