Align Light to Object
 

It's me again :>.

How do I add a lightsource exactly in an object (i.e. a light bulb)? Or do I have to move the light manualy in position?

For that type of light it looks like a spotlight would work good. I would add a spotlight to the scene and move it into position right over your modeled light then parent it to the object useing the scene editor. When you move/rotate the object the spotlight will move with it.

One thing that can save you time in a scene is to use Luxigons. In modeler under the construct tab in the additional dropdown list, you choose add luxigons. Use the following link to a luxigon tutorial and you can see how it can save you lots of time setting up many lights.

http://pro.wanadoo.fr/benjamin.chape/tuts1.htm