step one: remove all clothes.
step two: put on old rain coat
step three: go out in public and randomly open coat at unsuspecting passers by.

sorry couldnt resist.
but yeah it is really quite easy. you can use the software updater from the nokia website as one option. this has all the instructions you need with it. but if you do really want a walk through check out the wiki like noobmonkey suggests. hope i didnt offend by the way.