This page outlines how to create your own set of API keys for use with the YouTube add-on.

Sign in at https://console.developers.google.com/
NOTE: youtube.com/activate and google.com/device go to the same place.

Configure the Add-on
The final step is to add your keys to the YouTube add-on, this can be done using one of the following methods.

Method 2
Configure the add-on:

Settings -> API -> Enable personal API keys = ENABLED
Settings -> API -> API Key = BLANK/EMPTY
Settings -> API -> API Id = BLANK/EMPTY
Settings -> API -> API Secret = BLANK/EMPTY
Enable the api configuration page, to enable this go to the Settings - API and enable Enable API configuration page

You should then be able to update your keys by visiting http://<IP of Kodi device>:<port>/youtube/api
The port used is Settings - HTTP Server - Port which by default is 50152

You can bookmark the results page for quick updates in the future. Be sure to disable this feature after use.