Winder handles are held on by a thin metal horseshoe clip. If you pull the bottom of the handle out slightly (with the handle pointing down), you will see it.
You need something pointy to lever it out - a sharp knife or something for added danger. As the clip flies past your ear at 500mph, try to catch it.
If you might need to take it off again, the winder will quite happily sit on the spline without refitting the clip. They are a pain to get out, so don’t do it more than you need to!