where to add web player playback engine in unity folder???

I have recently downloaded Unity 5.5.2f. While completing space shooter tutorial, I realised that unity download assistant didn't contain the web player playback engine... I manually downloaded the web player from **unity3d.com/webplayer** , but i don't know where to place it in the unity installation folder..... Can anybody tell me, please....................!!!!!!!!!!!!!!!!!!!!!!