Face licking is a greeting between puppies and their mothers. It's a form of saying "I love you, and you are my family."
They also lick our faces because, let's face it, there's good smells for a dog there. Our mouths are there....food goes in our mouths....food smells good... You get the idea. :)
Most people find it annoying, however, as it certainly is not a human greeting!!! You stop it through training. I would first try to redirect your dog away from the behavior. For most dogs (but not all) I would give a small, verbal negative marker said softly like, "that's wrong." Then I would give the pup a toy to chew instead and give a positive marker like, "But this is good. Yes!" When training pups, I have toys all over the house for quick redirection.
You also can try the ignore method. This takes time, but does work. When the pup licks your face, stand up and turn your back on them. Don't give any reward or punishment, just stand and ignore until the pup quits jumping or licking you. When it does, you can sit down and again give attention. When it licks your face again, same thing.
This takes patience because the behavior will actually get worse before it gets better. This is called an extinction burst, and you can Google it to read about it. Over time, the pup will get the message that all fun with dad stops when face licking starts.
This method works, but takes time and 100 percent commitment and consistency to get it trained. :)