HT4623: Update your iPhone, iPad, or iPod touchLearn about Update your iPhone, iPad, or iPod touch
Currently Being ModeratedNov 21, 2012 10:39 AM (in response to RayColes)
Welcome to the Apple Support Communities
This option is only available on iOS 5 or later. Connect the iPad to your PC and iTunes will ask you to update to the latest version. After update, you have to restore the backup in order to get back all the data
Currently Being ModeratedNov 21, 2012 10:40 AM (in response to RayColes)
The Settings > General > Software Update option only appears when you have iOS 5+ installed, if you have iOS 4 as your tagline suggests then you will need to do the update via your computer's iTunes.
Connect the iPad to your computer's iTunes and copy any purchases off the iPad to your computer via File > Transfer Purchases (that should copy all your iTunes purchased films, music, apps etc). You may also want to copy photos and any important documents off the iPad as well e.g. via the file sharing section at the bottom of the device's apps tab when connected to iTunes, via wifi, email, dropbox etc - they should be included in the backup, but it's best to have a copy of them outside of the backup just in case. You can then force a backup of the iPad by right-clicking the iPad 'Device' on the left-hand side of iTunes and selecting 'Backup'.
Then start the update by selecting the iPad on the left-hand side of iTunes, and on the Summary tab on the right-hand side clicking the Check For Updates button
Updating to iOS 5+ : http://support.apple.com/kb/HT4972
A first gen iPad should update to iOS 5.1.1 (it doesn't support iOS 6).
An iPad 2 and 3 should update to iOS 6.0.1, so you will lose the built-in YouTube app and the Maps app will change.
Currently Being ModeratedNov 21, 2012 10:41 AM (in response to RayColes)
iOS did not intruduce WiFi based updates until 5.0. The only way you will be able to update from 4.2 is by connecting to iTunes (once you have updated, future version can be downloaded directly to the iPad via WiFi).
Before updating, back up the iPad, and transfer purchases over. You should also consider downloading those purchased movies to iPad as a matter of course.