I am going through the sirius installation procedure attached to this thread but am having trouble at step 3. How do you remove the retainers so that the plastic bin can be removed behind the back panel? They don't appear to turn to loosen or be easily able to be lifted. I have tried to gently lift them out but they don't seem to be giving way. I do not want to break them so I am hoping there is a simple method. Thanks in advance for your help.