Dig out a trench around the lawn or landscaping areas. It needs to be slightly wider than the material you are using for the curbing. Measure how deep the curbing material needs to go in the ground and dig the trench to that depth.
Check to ensure that the trench is level if you are working with a fairly flat lawn area. Use a level in the trench. Dig out higher areas and fill in lower ones with the dirt you originally removed from trench.
Place the curbing material in the trench so that each piece is up against the next with not gaps in between. One of the main purposes of curbing is to keep grass from creeping into landscaping and to keep weeds from coming into the yard. This is why you bury part of the material below ground and why there should be no spaces.
Fill in around the curbing with the dirt you dug up and tamp it down to secure the curbing stones in place.