Worries, conerns, and preparations before Japan

Hey guys,

New thought, a few friends of mine recommended that I get a hanko before I leave. Well, it turns out that I already have one that I received earlier as a graduation present (I didn't know what it was then, but I do now haha). The box is rather inky everywhere, I'm not sure if something happened to it earlier if they shipped it from Japan, but it seems to be ok.
To be honest, there's a kanji I don't know imprinted on mine, but I'm assuming it's either my name in kanji (doubt it, my last name doesn't sound japanese) or a generic one. From what I've heard, the hanko is just like an official stamp people use on their documents. But I also heard that it needs to get registered etc. for it to be actually used.

So this is my query: I'm really not sure what good a hanko would do me as an official document seal if it's mass printed and it most likely doesn't have my kanji name on it? I'm confused how people will know that whatever document I stamp would be mine versus someone else's. Maybe I'm missing something in all this, but is anyone willing to clear this up for me?