Hi Christian, welcome.
This is just a simple matter of extracting the face you want and pasting it onto the target head.
Of course, there ARE a few
other steps needed to make it really fit the new head.
Here's the gist:
1) Copy as much of the new face as possible. Don't worry about exactness, a layer mask will solve that overflow problem later.
2) Sometimes you may have to flip the face over for perspective matching, or even Skew it a little (
using the Transform filter).
3) Add a layer mask to the new face layer and using black, paint out all areas (
particularily around the outer edges) that don't belong or overlap the target head incorrectly. Use medium to small soft edged brushes for this. And zoom in very close to be as precise as you can;
this is usually needed for getting between bangs, etc.
4) Use the HUE&SAT filter on the new face to match skin tone. There are other methods for this but i've found that most often only a slight adjustment to the Lightness &/or Saturation settings are needed. But this part is really dependant on how similar the new face is in tone to the target/original face. If it's too extreme, you could end up having problems that will be unfixable.
Can you tell me which face was cloned in this photo? I think i made it somewhat obvious.
And if you know, take note of how the new face was altered/adjusted to fit the new head.
Integrating a face on a other picture..? 
Linear Mode
