To use HDR Light Studio with V-Ray, use ActiveShade with V-Ray RT. This way you can see interactive updates in V-Ray RT as you light using HDR Light Studio.
Hidden Area lights are still rendered by default by V-Ray
Go to the Production Render Mode settings
Switch to the VRay tab
Expand the Global Switches section
Check the "Hidden Lights" setting
Issue: If non-physical settings are created by HDR Light Studio, warnings can be shown
Go to the ActiveShade Mode settings
Switch to the V-Ray RT tab
Expand the V-Ray RT section
Untick the "Warn for non-physical settings" setting
These are the manual steps needed to create an image based lighting setup that is compatible with HDR Light Studio.
When HDR Light Studio creates an IBL Hook for you, it generates this setup.
Create a V-Ray Dome Light, ensuring Spherical (full dome) setting is On.
Enable Use Texture on the V-Ray Dome Light properties, and then choose a VRayHDRI in the Material/Map Browser. View the properties of the VRayHDRI in the Material Editor, and ensure Mapping type is set to Spherical.
HDR Light Studio will now see and connect to this IBL setup.