The search is automatic when you select Duplicate Skin Search.
When you do it will search every texture (*.bmp), mesh (*.skn), and mesh
configuration file (*.cmx) that appears to be valid for use with skins. The
resulting list is cross referenced to locate duplicates. Keep in mind the only
thing compared is file names. Some duplicates could be intentional to replace
game defaults. Usually you will know this already though I hope. As you can see
I have quite a few in ExpansionPack3\SkinsBuy. That is because Sims Deluxe added
the ExpansionPack3 set back in after Sims Vacation made a copy in
ExpansionShared. These folders have the same content in both of them. Or are
adding bloat to my game for no reason. To fix this I will just delete the
ExpansionPack3 set but you can either do that or move them into storage and out
of the game. To do this just double click the duplicate and it will be placed
into a mirrored location with the same path but a different root. Both the
original root path and the destination root path are also displayed. If you find
you need to put any files back where they were just double click the file in the
storage window. The description window shows the details about both files that
are duplicated.
Note: If the duplicate is in a far file then it
can't be moved. You will either need to leave it as a duplicate (The one outside
of the far will be used) or you can move the one not in a far to storage. This
will most often happen when either a default is distributed with skins
unnecessarily or when a duplicate is used to override defaults in the game.
(Files not in *.far files will always override ones in *.far files if they have
the same name and it is not just limited to skin files. Objects, npc's,
neighborhood screens, etc. can all be overridden this way as long as the paths
used are valid)