Connect your iPad to your computer and launch iTunes. You'll most likely be prompted to update. For more information and full details, see the section titled "Update your device using iTunes" in this support article:
You should read this article as well:
Forum Tip: Since you're new here, you've probably not discovered the Search feature available on every Communities page, but next time, it might save you time (and everyone else from having to answer the same question multiple times) if you search a couple of ways for a topic, both in the relevant forums and in the Apple Knowledge Base, before you post a question.