Frog kicking is simple in theory. Bend your knees to bring the feet closer to you butt. Then push the feet back and outwards, and finally pull them forcibly together. As you
squeeze the water between your legs, you glide forward. Fins will make this even more efficient, especially if you can rotate your ankles a bit (which is lovely with bare feet in a pool too). This is best practiced in the shallow end of the pool as your friend is watching and giving feedback. Keep your hands on the edge and only pay attention to leg movement. What is important is a) symmetry of movement and b) the feel that your legs actually grab and push the warter. Something like this:
And buy new fins. Doing back kicks and helicopter turns are next to impossible with split fins. I won't accept AOW students with split fins
Feet are not needed for turns and reversing. There are at least two ways of reversing with hands: the reverse breaststroke (inwards) and the palm propeller movement (needs less space sideways but is quite physical). Legs have stronger muscles and are often preferred for reversing. With your fins however, maybe not. The reverse kick also works without fins as your legs grab the water. Split fins have their plusses, but especially cave divers dislike the line trap in the middle. For accurate turns, the palm is wonderfull. Just note that it can be both horizontal and vertical. Move the hand horizontally, turn it, and push the water sideways. Repeat. Legs, again, are stronger, and often preferred. I actually reverse and turn on a weekly basis using hand techniques in a pool while freediving and dwelling on the bottom. Whatever gear you have, learn to use it, and avoid environments where the gear poses a risk. Split fins can be great, or they can kill you, but so can a tasty bit of beef.
Why on earth would you
need the frog kick? Are you planning on becoming a cave diver who is sometimes forced (by the ceiling) to the close proximity of a muddy floor, and must thus direct the thrust sideways to avoid ending up in a mud cloud? If you dive in an ocean where there is twenty feet (or a mile) of water then it really does not matter how you kick. The flutter kick is simple, easy on the joints, efficient, and powerfull. And near the bottom it lifts a cloud of mud, but...