This modifier creates coordination polyhedra around selected atoms/particles for visualization purposes. A coordination polyhedron is the convex hull spanned by the bonded neighbors of a central particle.
Note: The modifier creates coordination polyhedra only for currently selected particles. So you should select some particles first, e.g. using the Select particle type modifier.
The modifier requires bonds to determine the neighbors of a particles. Thus, you should create some bonds first using the Create bonds modifier (unless they are already provided in the input file).