When we talk about "winning" NaNoWriMo or Camp NaNoWriMo, we are talking specifically about the global writing challenges we run in November (NaNoWriMo) and April/July (Camp NaNoWriMo). To "win" NaNoWriMo or Camp NaNoWriMo, you have to be officially signed up for these challenges within our system and reach your word-count goal by 11:59 PM on the last day of the challenge. This can be achieved by manually entering your total word count where it says "Update Total Word Count" in your novel box, or by typing enough words into the writing space (depending on which preference you set) to reach your goal. For official event challenges, when you win, you'll be taken to your winner page, where you can watch the winner video and download some swag.
You can still "win" other writing challenges, whether they are class challenges created by your teacher or a writing program you participate in, or whether the are independent challenges you've created yourself. Meeting your goal = winning, no matter how or when you participate.
And, if you don't reach your word count goal on the timing you intended, don't be discouraged. The most important thing is that you showed up to do something amazing and that you keep on writing!