This installation guide should be used when the batteries for the radio are out of power and new batteries need to be installed. The troubleshooting guide for this process can be found here.
First, apply pressure with your thumb on the top of the battery cover.
Next, pull down on the cover until it begins to slide.
Finally, once the cover is completely off, pry up the old batteries with your finger or a strong, skinny tool (i.e. spudger).
Put the new batteries into their slots in the back case.