Move your mouse around to aim the angle of your shot, while holding down the left mouse button will add power to your shot. Release the left mouse button to swing. Since the power meter won't decrease after holding down the left mouse button, press the CTRL key to decrease your shot power at any time. The M key toggles the menu, the S key toggles sound, and the T key toggles a menu that will give you tips on the game.
Kingball offers a lot more than your average online golfing game - for starters, there's a huge variety of modes to play through, each giving a unique challenge. Easy mode will give you more forgiving physics, and the ball will roll less, but you'll have to wait until the ball has stopped moving before you can shoot it again. Normal mode is basically normal, you'll be earning more points for choosing it, and in hard mode you'll be gaining the most extra points while dealing with unforgiving physics - the plus side on this latter mode being that you can take a shot while the ball is still moving.
But those aren't the only modes you'll have to choose from - initially, before choosing a difficulty, you'll be able to pick one of three courses - these also progress in difficulty, but each has its own unique challenges that are worth checking out. Once you've actually started playing a hole, you'll see what Kingball is really about.
The goal of each hole you're on is to get the golf ball to touch the pin - this can be accomplished in a variety of ways, since you can just ricochet the golf ball off of every wall in the room, or since you can take a conservative shot and let gravity do the rest. It should be mentioned here that the effect of gravity in Kingball, unlike most other golfing games, is very immediate - so keep it in mind before taking a shot.
Once you've made a few shots, and scored on a few holes, you'll know what you're doing with Kingball. It's a fun, enjoyable game with tons of different modes to play through - if you're bored with one, just try another - you'll almost never run out of different modes to choose from.