Are you asking how to get the needle plate off to clean underneath it. On the Berninas I have seen ( I have a different model) There is a little circular marking on the needle plate that looks a little like a target. First remove the needle and presser foot, then press down firmly on that circle and the needle plate should just pop loose and you can pick it up. Then just press/snap it back in place when you are done.
Let me know if you need a picture.
Edit: I found a video for you!
http://www.youtube.com/watch?v=hJCRfpO_MVo