I am asking specifically about the little plastic cover over the back lens. My photos aren't clear and I assume it's due to that cover. I have no idea if I should remove it and how this can be done.
Keep the hard plastic cover.
Remove the static-cling plastic sheet used during shipping.
Is there any physical damage to the plastic cover?
Can you link us to an unedited example photo with all the EXIF data still in it so that we can see what you are seeing?