Assuming you mean the 6x9 speakers in the rear deck then: You should be able to access it from the trunk area. In the trunk there are 3 screws holding down the grill over the speakers. Remove the three screws then go to the back seat and you should be able to get to the screws that hold down the speakers. Be sure to unplug them first and then remove the speakers and install your new ones. Its very simple to do.
Hope this helps.