After these awesome videos, you now know how to start a startup. Next up: grow the startup. There is lots of good reading on growth (like this post by Paul Graham from 2012, which is still super valid: http://www.paulgraham.com/growth.html). But since you are looking for videos, you should check out the free video on Growth Hacking by Mattan Griffel on onemonth (also a Y-Combinator company - http://mbsy.co/cs72Z).