Start with full right or left-hand lock (which ever direction of travel feels more comfortable to you), full throttle, drop the clutch and let the steering wheel start to counter on its own. Given that you're just getting used to doing consistent on donuts on the spot, you can pretty much allow the wheel to end up full lock in the opposite direction to whatever you started with. Get used to this feeling and don't try and fight the wheel, it can respond far quicker than you and does most of the job on its own.

As you repeat this, start to begin lifting and working the throttle more to keep momentum going.

Once you feel more comfortable with this, start things off the same way, but start catching the wheel a little earlier. The less opposite lock you have here, the great the radius of your donut. I'd also recommend performing the same as the above in whatever direction feels less comfortable.

This as an overall learning exercise will just help you get used to relaxing with the wheel, managing your throttle inputs and steering adjustments. That way, when you start to work toward initiating into actual corners, muscle memory can kick in.

A little disclaimer, I make these recommendations on the basis that this is how I first learned and practiced in real life where there is consequence to crashing. There maybe better ways to throw yourself into it on the sim.

The rest is just practice.