This product requires the free installation of at least one of the smart head props of 2nd face that are available in my freebies section on Renderosity:
https://www.renderosity.com/users/3Dream/freestuff
After adapting 2nd face to the figure you are working with, simply go back to the 2nd face POSE directory and you will find a folder named Anne MATs.
It is within this folder that you will be able to choose between 60 skin tones so that you can find a tone suitable to your scene.
NOTE: In the Materials directory you will also find the same MATs but in my opinion, you can use them when you intend to use 2nd face as a independent prop, that is, without adapting it to a figure.
If you have any question about this product please contact me. Thank you.