Many landscape lights come with an attached plastic spike so you can install them in the ground. But not all ground is soft enough to easily drive these spikes. Using an auger bit you can drill out a hole to hold your lights.
Impacted dirt of any type will hinder the installation of these lights. So grab your cordless drill and auger bit, which will drill right through the toughest of dirt surfaces. Work your drill in an up and down motion to help clear the dirt, then drop in your light.
A landscape lighting spike needs to sit about 15-20 cmbelow the surface of the ground. This depth will be enough to hold the light securely and keep it from tilting and falling out.
Install Landscape Lighting Into Caliche [Charles & Hudson]