Layman's terms ....
Victoria 4 contains many magnets that replace a lot of the old JCM (joint controlled morphs) that previous Daz figures had to make them bend better. Using the !Magnetise To V4 adds these magnets to your clothing so that it bends better as well. You do not manually adjust these new magnets, they are tied into Victoria 4's joints so that when she bends a particular way, certain magnets are activated to make that bend better.

Magnetise DOES NOT add morphs to your clothing, make other character fit into your clothing, add full body morphs to your clothing, give you the ability to dial her boobs up to gigantic proportions and get no poke thru, clean your dishes or make you coffee :)