To add Displacement to your geometry, you first need to set up a material network with a PxrDisplace as shown here, and once done, you will also need to add displacement settings to the geometry.

These parameters can be found under RenderMan > Prototype Attributes > Shading > Displacement and at a minimum, primvars:displacementbound:sphere needs to be set > 0. 

If tearing occurs, select Smooth Normals and Smooth Displacement under Prototype Attributes > Geometry > Polygon.