First make sure you have the latest version software on your iPad & iTunes.
Second, as Winston said, whenever you play music or video on your iPad you should be able to see an airplay icon on the right of your volume bar. Touch that & select your Apple TV. Like magic you will now be listening/watching your content on the big screen!
Next check out this link http://www.apple.com/itunes/remote/ it will explain how to use Apple Remote, a free app that lets you connect & control your Apple TV.
The Home Sharing feature is used for streaming your content from your iTunes library to your Apple TV. You need to enable it on both your computer & Apple TV. If you can't see where, check out help on iTunes, it will light the way!
Hope all this helps, I think Apple TV is a great addition to your home & I'm sure you will love it once it's up & running.