You need to include this jar in your project. Copy and paste this jar in libs folder and don't forget to add it in gradle file
dependencies {
compile files('libs/YouTubeAndroidPlayerApi.jar')
}
Clean and Build your project.
Now you're ready to use the YoutubeAndroidPlayerApi
For playing an youtube video, you need to have video id corresponding to it so that you can play it on youtube.
For e.g : https://www.youtube.com/watch?v=B08iLAtS3AQ, B08iLAtS3AQ is video id which you need to play it on youtube.