The article below may be able to help you with this issue.
Click on the link below to see more details and screenshots.
I've quoted some helpful highlights for you:
Trying with one device as a time, see if you are able to setup Airply mirroring with your iPhone:
To use AirPlay Mirroring, you will need the following:
- iPhone 4S (or later), iPad 2 (or later), iPad mini, or iPod touch (5th generation)1
- Apple TV (2nd or 3rd generation)2
- Wi-Fi (802.11a/g/n) network
Enable AirPlay Mirroring
- Connect your iOS device and your Apple TV to the same Wi-Fi network.
- On your iOS device, double-click the Home button to display your recently used apps.3
- Swipe the recently used apps twice from left to right until you see the AirPlay icon: If you do not see the AirPlay icon on your iOS device, your iOS device and Apple TV may not be on the same network. Get help troubleshooting, if necessary.
- Tap the AirPlay icon to display a list of available AirPlay devices.
- To use AirPlay Mirroring, select the name of your Apple TV, then toggle the ON/OFF slider to ON.
I hope this information helps ....
Have a great day!