What you are looking for is the Youtube API’s loadVideo method. From the docs:
public abstract void loadVideo (String videoId)
Loads and plays the specified video.
You can use it like this:
@Override
public void onInitializationSuccess(YouTubePlayer.Provider provider, YouTubePlayer player,
boolean wasRestored) {
this.player = player;
player.loadVideo(video.id); // where video.id is a String of a Youtube video ID
}
In a similar vein, there is also the cueVideo
method, which adds the video to the playlist, but does not automatically start playing the video.