one of the first things is to ground yourself. Doesn't have to be a full ground, just a quick centering of yourself.
As you breathe in, curl your hand, or hands, if you want to use both, into a fist. As you breathe out, expand your fingers into a cupped claw, and imagine your energy, ki, whatever you want to call it, form the ball the palm of your hand. You might have to do this breathe in/out phase multiple times at first. That's okay. Just imagine on the second breathe in and beyond that the energy in the ball is retracting back into you.
Once you have a ball, you can maintain with simply holding your hand in that gripping formation, which may start to strain your hand, and breathing normally.
The ball will be small at first, and may even blink in and out of existence. But, with practice, it'll get bigger, and brighter, and stay longer.
You can mix spells with this ball, such as healing, and send the ball to where it needs to go. Throwing it is what I usually do.
Others might have other methods, but this is the one I use, and it works just fine.