How to download air play to my iphone 5s

Good day to you,

I was trying to use a projector in my iPhone 5s since I saw a YouTube video about usage of projector and mirroring system, and after that I just download a projector Apps from Apple store by free and trying to start using but because of AirPlay I cannot use it, so please I'm requesting you to give an advice for usage of projector

Thanking you