there's a row of bolts, 4 or 5 each side, underneath. the glue is a thin strip on the top edge and can be pulled away.
on mine the glue had parted from the plastic but was still firmly stuck to the car. you can get a tool called a caramel wheel which goes in a drill and will remove the glue from the bodywork. the wheel is harder than the glue but softer than the paint, it wears away as it removes the glue whilst leaving the paint undamaged