Drop an .hdr or .exr file on the script to create a VRay Dome Light. If a VRay Dome Light already exists in your scene, it will update the HDR map. You can display it in your viewport in one click, and access the main parameters as horizontal orientation, overall and render Multipliers. The separate Light & Background button will create a second Dome Light, to separate the VRay Dome Light that illuminate the scene and the one that show as a background