Do you mean that your iPad is running iOS 4-something? If yes, the only way you can upgrade your iPad is to connect it to iTunes and select the Upgrade button (on the main Summary page). The over-over-the-air updates don't work for those who are not on iOS 5 or higher.
Which reminds me. You can't upgrade to iOS 5.1.1 any longer (Apple is no longer approving that version). When you upgrade using iTunes, you will upgrade to iOS 6, which is the newest, Apple-approved iOS.
Hope this helps. Holler back if you need more assistance.