To use AirPlay without WiFi, you have to enable Bluetooth and WiFi first. Then go to your Airplay app and from the "Airplay status menu select Airplay 2 compatible TV", which should be located in the top right corner of your iPhone or iPad. Now, for the iOS device connectivity, "select Airplay" from the control center and place the code you're asked to. After the following steps, you can use your AirPlay without WiFi.