phpBB ACP Style Extension

Install

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

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