Hi there...I just deleted your other post as it was a duplicate of this one. Please do not do this since it makes it hard for other members to read and help you of there are multiple threads of the same topic present. It is also against forum rules.
I have also moved your post to the Help section.
To update your iPad...from 4.3 to 5.1-you will need to connect your iPad to your computer update it that way. Make sure that your iTunes is updated to the current version before beginning the update.
Also have a look at this thread. This is old, but may be helpful for you to look at.