1. Read at the end of this
2. Download AdvancedEditing.sh3p file from here
3. In your home directory (under linux) IF you have run at least once the SweetHome3D program you will find a hidden directory .eteks.
In this one you will have the directory sweethome3d .
There if you don't have allready a directory name "plugins" you must create it.
4. In this directory you have to copy the AdvancedEditing.sh3p file.
5. Restart the SweetHome3D program.
P.S. My SH3D is also .tgz [:)]
PPS My path is /home/dorin/.eteks/sweethome3d/plugins/