This article goes over how to save a household to the Library and Share or Export them.
1. At the Edit Town Menu ...
Where you see the town in the background, Find your family's house. Left Click on it, and select either the folder button, or the arrow with a star above it button.
Click the Share button to "share" the family. This will add the family to the library and will save a copy to your Exports folder.
-- The Arrow with a Star above it: (Share button) Saves the file as a .Sims3pack file which can be found in the Export folder. This will also save a copy to the library. [\Documents\Electronic Arts\The Sims 3\Exports]
-- The Folder: Saves the file to Library only. - A file that contains the family can be found in the Sims 3 library folder. [\Documents\Electronic Arts\The Sims 3\Library] Click the modified by to see the most current file.
Either of these files or entire folders can be backed up to a usb key or other backup media of choice.
Once you click either the Folder button or Share button, a pop-up menu will appear and say: Current interactions for all Sims in your town will be cancelled if you do this. Would you like to continue? Click X, for no or the Check mark for yes.
2. Saving Household Only or Household with House.
After that a pop up message lets you know the export was successful and to open launcher to upload and share to the Sims3.com site.
Again, if you use the Share button, you can find the file in the .Sims3Pack format in the Exports folder: [\Documents\Electronic Arts\The Sims 3\Exports]
No need to upload to the Exchange to share your Sims family.