I havent used the grog build but looking at it it is similar to Infinity, go to the download section all the instructions are there for Wooshbuild infinity or grog build,
Make sure you take a copy of the line details before re flashing an image,
You can also upgarde to 6.2 from your current box,
Menu > setup > Software management > Flash on line / Local > Green button for on line and select the latest 6.2 image.