DAZ|Studio has a default light, a distant light shining from the camera, that switches off as soon as you create a real light. Point lights have quite limited range at the moment - we're all hoping they will be made more powerful and adjustable before version 1. To light the ground you need a light shinging onto it - the glancing illumination from the default light isn't picked up: generally either a spotlight or a distant light would be used, unless you want a fairly low-key image. You can look through the directional lights (pick them from the Camera/View menu at the left of the Viewport's title bar) which makes aiming easier.