All of them are available as YouTube videos. If you only watch one, I recommend the fourth.

https://www.youtube.com/watch?v=ielZBraKsw8

https://www.youtube.com/watch?v=sabeq-FtfGw

https://www.youtube.com/watch?v=OE_UNZW-4_U

https://www.youtube.com/watch?v=JtgQJT08J1g