I like the idea of flipping the ball over the “C” or backwards C if you are right handed. Your thumb should be pointing towards your ear.
Next, buy a nerf ball, and practice getting the ball to roll out of the horseshoe with overspin. This means the heel of your hand is leading-no wrist snapping yet! Just get used to the ball rolling out. When you get the sensation right, you can graduate to a baseball. Start as another poster suggested short toss with the right spin (overspin) on the ball. Do not worry about the break at this point (although it might). Proceed back until your at 60 feet 6 inches. After this go to the mound and repeat. Now perfect your release point. Still NO wrist snapping.
Now after all of this is mastered, Think about arm swing and wrist snap. In a fastball you are driving toward the plate, like you are throwing a spear. With the curveball you want just as much effort, but think of a more rounded delivery. Instead of a very low arc like on a fastball think more about a 1/3 of a rainbow arc (or a 1/2 rainbow arc if you are throwing a changeup off your curve which comes much latter). But you are still swinging your arm with maximum effort, the energy is directed differently though. Now add wrist snapp which is like turning off a light bulb on a string switch. Keep ypour wrist in a neutral position.
Now learn the release points to either front door the ball or make it dive low and away. You’re on your way.
If I have not been concrete enough let me know and I will try to help, Ian.