Angular gradients build on the circular nature of a radial gradient, but allow various colors to be built into the gradient. Think of this more like a linear gradient wrapped around a circular shape, great for things like color wheels.
To apply a solid color or gradient fill to a shape or path, select the shape or path and navigate to the Properties Inspector in the Appearance section. Clicking on the Fill color picker will open a popover where you can select any color or enter a hex color value.
At the top left where it says Solid color, click on the dropdown and select the desired option to switch to a gradient fill. Once the gradient fill of choice is selected, clicking along the gradient will add additional color stops, and selecting any points will allow you to modify the color and opacity at that point in the gradient.