Please how to update my iPad to iOS 6 ?

Update it from iTunes on a computer as described at the bottom of this article. If it's running an iOS version prior to 5.0, there won't be an option to update from the device itself.

The original iPad can't be updated past 5.1.1.

(80218)

If you have an iPad 1, the max iOS is 5.1.1. For newer iPads, the current iOS is 6.1.3. The Settings>General>Software Update only appears if you have iOS 5.0 or higher currently installed.

iOS 5: Updating your device to iOS 5 or Later

http://support.apple.com/kb/HT4972

How to install iOS 6

http://www.macworld.com/article/2010061/hands-on-with-ios-6-installation.html

iOS: How to update your iPhone, iPad, or iPod touch

http://support.apple.com/kb/HT4623

If you are currently running an iOS lower than 5.0, connect the iPad to the computer, open iTunes. Then select the iPad under the Devices heading on the left, click on the Summary tab and then click on Check for Update.

Tip - If connected to your computer, you may need to disable your firewall and anitvirus software temporarily. Then download and install the iOS update. Be sure and backup your iPad before the iOS update. After you update an iPad (except iPad 1) to iOS 6.x, the next update can be installed via wifi (i.e., not connected to your computer).

Tip 2 - If you're updating via wifi, place your iPad close to your router to preclude getting a corrupted download.

 Cheers, Tom 😉

Easy.

On iPad: Go into Settings>General>Software Update> and tap Update or Download.

On computer: Open iTunes>Connect iPad via charging/adapter cord>Go into the device overview>Hit Check For Update> Update