At the beginning is the only proper way. If you really didn't want to, I know that the anime of part 4 does a pretty good job of introducing you to it. But you'd be missing the first 3 parts and that's kinda uh. Well yea, it's doable but not entirely recommended.
Almost forgot, but part 7 is the most ok part to just start with as it doesn't directly connect to any previous part. But there are still things you'd enjoy more from having watched the previous parts.