This is a note, as Google Ads changes often. Below is how you start a new Ad on Google Ads as it seems difficult to figure this out.
All you need to do is hit the blue PLUS button from your campaigns page -
A new pop up opens and you click + New Campaign
After this you just follow the process which is very straight forward, with its own set of challenges. Pretty soon you should have your Google Ads up and running on not just Youtube but any Google platform!