Angular gradients build on the circular nature of a radial gradient, but allow various colours to be built into the gradient. Think of this more like a linear gradient wrapped around a circular shape, great for things like colour wheels.
To apply a solid colour or gradient fill to a shape or path, select the shape or path and navigate to the Properties Inspector in the Appearance section. Clicking the Fill colour picker will open a popover where you can select any colour or enter a hex colour value.
At the top left where it says Solid colour, click the drop-down 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 colour stops and selecting any points will allow you to modify the colour and opacity at that point in the gradient.