I tried it yesterday and I got error messages
Probably I was doing something wrong, so I've already sent a message to him.
It's not particularly difficult.
You go to
https://console.developers.google.com/ and enable the devkit or something if you haven't done so before. Search in the library for the Youtube Data API. I don't know what options are given, but there's an option to enable the API or something. It will probably ask some questions, doesn't matter, default options were fine I think. If everything worked, you will find the API under credentials when you're done. There's a button to copy the key, click it. Put it in this command (replace {key}, not the apostrophes (although it should work without them)):
gapi.client.setApiKey('{key}')
Now copy that command and go to plug. When you're logged in press F12 to open the console of your browser. It should give you a command line at the bottom of whatever text the console holds. Enter the command, press enter to run the command and it should return 'undefined'. Ignore that, it should work now. Try it out and bask in the glory of your own IT skills.
There's a limit to the amount of usage an API can get per day. It's like 10k requests. That isn't all that much if multiple people are using the same key. Getting one for yourself is better. I don't know how long the key stays valid.