I don't have a software update tab under settings. How do I find it?
Software update was not introduced until iOS 5. Your iOS must be older.
Update your software using iTunes.
Update its OS from iTunes on a computer to add the tab.
Updating needs to be done through iTunes .HT4623 How do I update my iPad?: Apple Support Communities and iTunes 10 for Mac: Update and restore software on iPod, iPhone, or iPad
Go to Settings -> General -> Software Update. This is only for iOS 5.x and newer. If you go to Settings -> General -> About and tell us what you "Version" is, that would help answer your question better.
See the information previously posted in the thread.
Connect the iPad to the computer, launch iTunes. Select the iPad under the devices heading on the left, click on the Summary tab and then click on Check for Update
I've updated iTunes but there isn't a device heading on the left
In iTunes' menu, click View > Show sidebar
Retrieving data ...