The V4 clothing magnets by Lyrra work on any clothing. They come with instructions on their usage.

If you mean the magnets that come with V4 herself, they are not magnets you need concern yourself with. They are simple replacements to the old JCM system and only need to be 'magnetised' to the clothing you are using via a special pose file included in V4's purchase package. They do not make full body morphs, nor do they make other character clothing fit V4.