To use preview for glass, you need to sideload the apk file onto Google Glass. Here's a brief reminder on how to sideload. Put Glass into Debug Mode From the "ok glass" screen... - Scroll "back" to Settings. Tap. - Scroll "forward" to Device Info. Tap. - Scroll "forward" to Turn on Debug Mode. Tap. Load the app onto Glass - Connect Glass to your computer via USB cable. - Get the Android SDK and in