Replace the side panel, and screw in the screw on the front and back
Replace the cover panel, and screw in the single screw on the back
Replace the front panel, and screw in the pair of screws that hold it in place. Make sure all the metal clips are lined up properly.
Lower the CD Player module down into place, and screw in the two screws on each side. Everything should be nice and flush at this point. If anything is not, take it apart and try putting it back together again.