Youtube Videos Gallery Extension

Install

Download the latest release.
Unzip the downloaded release, and change the name of the folder to youtubegallery.
In the ext directory of your phpBB board, create a new directory named dmzx (if it does not already exist).
Copy the youtubegallery folder to /ext/dmzx/ (if done correctly, you'll have the main extension class at (your forum root)/ext/dmzx/youtubegallery/composer.json).
Navigate in the ACP to Customise -> Manage extensions.
Look for Youtube Videos Gallery under the Disabled Extensions list, and click its Enable link.

Navigate in the ACP to Customise -> Extension Management -> Extensions.
Look for Youtube Videos Gallery under the Enabled Extensions list, and click its Disable link.
To permanently uninstall, click Delete Data and then delete the /ext/dmzx/youtubegallery folder.