How do you enable playback API? I have mini player window>I go to full player>then to settings. But i don't see "desktop settings" or anything regarding Playback Api

Just trying to get a rainmeter skin to work, but i can't get gpm to communicate with it. The troubleshooting steps says first thing is enable playback api. I can't find "desktop settings" in chrome extension or browser settings. via /r/googleplaymusic http://ift.tt/2t5jxGy