Basic light

On both the Omni and Spotlight you can enable raytracing shadows.

Turn raytracing on the root and enable shadow casting on the light.

Set shadow map type to Ray Traced.

Area light

Turn raytracing on the root. Add an area light to the scene and set the light to ray traced in the attributes.

Once raytracing is enabled there are additional shadow attributes exposed.

Sky light

To enable raytracing in a Skylight, turn on raytracing on the root, then enable raytraced in the skylight attributes.
Once enabled additional raytracing parameters will be available.

The skylight is a traditional dome light to which you can add hdr 360 images via the Environment Map node for a more realistic raytraced lit scene.

Baked lighting

With all lighting, raytraced lighting can also be bake into lightmaps.