Instructions
Download the PlayX modification from GarrysMod.org.
Extract the downloaded PlayX zip file and place the ̶0;PlayX̶1; folder into the Gary̵7;s Mod add-ons folder on the server. You̵7;ll find the folder at ̶0;C:\Program Files\Steam\steamapps\User\garrysmod\garrysmod\addons̶1;, where ̶0;User̶1; is your Steam username. Look in the ̶0;Program Files (x86)̶1; folder instead if you̵7;re using a 64-bit version of Windows.
Launch Gary̵7;s Mod and start a server.
Open the spawn menu by pressing the ̶0;Q̶1; key while playing Gary̵7;s Mod. If you̵7;ve set a custom shortcut key for the spawn menu, press that key instead.
Click the ̶0;Other̶1; tab in the spawn menu that appears.
Click the ̶0;PlayX Player̶1; icon under Other to spawn the player.
Click the ̶0;Options̶1; tab on the spawn menu and click ̶0;Administrate̶1; under PlayX.
Type the Web address of the YouTube video in the form ̶0;http://www.youtube.com/watch?v=code̶1; into the URI box that identifies the Uniform Resource Identifier.
Click the ̶0;Open Media̶1; button to start playing the YouTube video.