To install just ..

1. go to Edit > Preferences...

2. on the left change the tab to "Add-ons"

3. top right click on "Install..."

4. select the face2FACE.zip you downloaded from here

Start playing around!

For a quick start select one face in a source object and one or several in the an target object and press F7.

Help with the shortcuts can be found in the n-panel of add-on during execution.

The whole documentation can be found on the face2Face website.