How can I clean the lens?

It IS possible, but not recommended...

First off, dropped in water now dry, appears to work fine, is the typical start of a hellacious long repair needs... I would just trade this in for a new one in my professional advice....

however if you want to do this,

Take off the back,

Take off the front,

Take off the main board on the back

Take off the LCD

Take off the LCD frame

Take off the top cover

Take off the front frame

Disconnect the lens unit electronics,

Now for the fun and VERY difficult part, I HIGHLY suggest just buying a lens unit as the lens has almost 8 ways it can go back together but only 1 is correct. Actually just buy a lens unit off ebay... usually only 30 or 40 bucks for this camera, IF you think the rest is okay... I would still trade in personally.