The back panel must be removed in order to proceed. Slide the cover so that it is fully extended.
The arrows in the picture indicate two small holes located at the top of the device. Insert a paper clip or a tack simultaneously into each of these holes and moderately push downward.
The springs will give as pressure is exerted. Once you feel this take place, pull down the cover with the paper clip/tack while continuing to push downward. This will release the back cover.