1) Paste the DIV codes on your website, where the video should appear to the users.
(Don't forget to change your video ID)
2) Place the JavaScript given in the reference image.
3) Place the CSS before the close of tag.
By doing this you can reduce the load of web pages.
Check The Reference For Complete Step By Step Process: https://codepen.io/Christaelrod/post/embed-youtube-videos-on-webpages-without-worrying-about-loadtime