The shutter mechanism is attached to the lens assembly with four tabs. The tabs clip onto the lens assembly at the four points indicated by the yellow circles.

To detach the shutter, gently lift the tabs using a plastic spudger.

Once all four tabs have been released, the shutter assembly will lift off the lens.

Once the shutter has been removed, the outer lens is exposed completely. This is a great opportunity to clean any fingerprints or anything else which might be on it. If you are extremely careful, the inner lens can also be accessed through the openings around the edge.

Three of the tabs are identical and of the type indicated by the red box. The fourth is of a different design but is released the same way.