I have installed a new Apple TV.My iPad & iPhone are on the same network.They do not connect to Apple TV.Do not understand!!

how is your network set up... i had a similar problem once when i was using my isp router/wireless modem... some modems .. like the TELUS actiontec seem to not allow airplay style connections... they also don't want you streaming from your computer to your xBox... anyway's after some research i found the solutions a little too hi tech for me so i just simply bought a new 3rd party wireless router... turned off wireless on my Actiontec and problem solved... don't know if this is the case with you or not

hope this helps

For airplay mirroring

http://support.apple.com/kb/HT5209

Enabling AirPlay from your iPhone, iPad or iPod touch

You can AirPlay videos, music, or photos from a variety of different locations on your iOS device, including from within the Photos, Videos, Safari, and Music apps,or directly from recently used apps.

To AirPlay video or photo content to your Apple TV:

1. Connect your iOS device and Apple TV to the same Wi-Fi network.
2. Open either the Videos, Safari or Photos app on your device.
3. Locate and tap the AirPlay icon (if attempting to AirPlay video content from Safari or Videos, begin playback first).
4. Select your Apple TV from the list of available devices that appears and begin playback.

If the above does not help, try to restart your router and apple tv ..