Hi Bill,
I will guess that you do not have OfB installed, so you will have to rely on doing things one of three ways.
If it is a custom sofa, then you can add it to a collection for commercial lots by using Jfade's Sims 2 Collection Creator - Version 1.1.1 at DJS Sims
http://www.djssims.com/ -- or add this to a collection in game - then edit the collection with the programme.
another way is to mod the file with Paladin's Sims 2 Categorizer from Paladin's Place
http://www.simwardrobe.com/lastly is to hack the file with SimPE and requires you locate the tutorial at MTS2 (I looked but did not locate it)