You just set the light on top of the lid behind where it hinges. You can cut the plastic portion at the back to accommodate a filter or heater cord.
ETA.. you don't want to put a canopy over a glass lid. You just choose one or the other. I've heard that glass lids are better because they have less holes and you can cut them to specially fit where your filter/ heater exit the tank. The light is more evenly dispersed through a glass hood.