On each client open your browser of choice and navigate to http://server:7782 or, if SSL is already working, to https://server:7783. Replace server with the real name of your server where you installed Lights-Out.

The browser will open the Lights-Out main page. Click on Installer to open the download page and click on the blue Mac button to download the installer package.

Download

Run the pkg file

Click Continue

Select location

Click Install

Installed

Finished. Now a new icon (the Lights-Out bulb) is visible on top.

Click on the bulb to open the menu:

Click on Preferences... and enter your server name and user credentials.