The 'Magnetize Clothing' files are mainly for use in Poser.

Victoria 4 was released with a pile of magnets rather than JCM's (Joint Controling Morphs), in Poser these magnets don't work on the clothing you have 'conformed' to her, which is where these files come in as they link V4's magnets to the clothing.

DS users don't really need them as we have an auto-magnetize function already built in, select "Edit > Preferences" and click on the "Content Library" tab, 'auto-magnetize' is either the 2nd or 3rd option.