This can be done by editing the fixture family in the Revit Family Editor and changing the light source type to “Photometric Web”. There are typically a few other steps that need to be undertaken as well.
The attached video (*.mp4 file) shows the process from start to finish. The following steps are illustrated.
1. Open the family of interest in the family editor.
2. Select the light source.
3. Open the "Light Source Definition" dialog.
4. Change the Source Type to "Photometric Web".
5. Adjust the "Tilt Angle" Type Parameter to the appropriate value. For a typical ceiling mounted fixture, -90 degrees is the correct Tilt Angle. However, the coordinate system that Revit uses for the Tilt Angle is undocumented (at the time of writing). As such, sometimes experimentation is required to determine the appropriate value.
6. Load the family into your project.
7. Verify that the photometric web looks correctly aimed. Both in Revit and in the Luminaire Manager preview window.
For additional information, please see the Autodesk documentation.