To use Airplay on your iOS device; Mac Air, iMac, or another iPhone, be sure that the Airplay receiver on your iMac or Mac Air is on.
Go to The System Preferences icon on your iMac/Mac Air
Under System Preferences, Tap Sharing Folder
Check the AirPlay Receiver to put it on, choose Anyone on the same network
Tap the Anyone on the same network button to proceed with the selection
The AirPlay Receiver is now ON.
On your iPhone, while watching a film on Reveel, you can see the AirPlay icon at the bottom right, tap the icon
Choose the device you want to AirPlay with
It will send a notification to the iMac/Mac Air and you need to hit Accept button to allow your iPhone to connect and AirPlay with the iMac/Mac Air
It will send an AirPlay code on your iPhone
Enter the code, then click OK
You should be able to watch through your iMac/Mac Air now.