Just checked an old one lying around - think they are cartridge not cup and cone?
Come on guys, throw him a bone. We all had to start somewhere.
Felix, those are cup and cone bearings, not sealed cartridge. And I would strongly advise carefully removing your disc rotor before your next step in this learning curve.
All the info you need can be found here:http://www.parktool.com/blog/repair-hel ... adjustment
And remember to use a cone spanner for the cone. A regular spanner won't fit in there.
The lock nut is right there, in the middle of your picture. The thing with 2 flat sides.