You need to do the following.
Add the furni to your hof_furni folder
Add the icons if you have them, if not rip them from the swf using a decompiler
Add the furnidata to furnidata.xml in your gamedata folder (You can copy & paste an existing furni). Make sure you change the class to the swf name & the ID to an unused ID in your furniture table.
Copy & paste a line from your furniture table and change the item id to match the ID you used in your furnidata.xml - MAKE SURE YOU CHANGE THE SPRITE ID TO THE SAME ID
Add to your catalog using catalog_items
Hope this helps