Review of how to form “f”: Keep your lips flat in a slight smile. Relax your upper lip so that you can see your upper front teeth. Place your upper front teeth lightly on your lower lip and push air out of your mouth, creating a friction. This is an unvoiced sound, so will not hear your voice when you say it.
Learn how to pronounce the "f" sound.
Click on the sound below that you would like to practice.