How to be exported to Luxrender using Graphicall builds.

I have downloaded a build from graphicall which has Luxrender in it. When i press “External” under the Renders Tab, in the Rendering Mode, and press F12, the render becomes all white and nothing opens up, despite the fact that i have clearyly set the Luxrender file directory. Why is this so? I use Blender 2.57.1 and Luxrender 0.8 RC4

Did you set external type to Lux GUI?

yes, i have done that

its ok. I’ve found it. I did not turn on “Run Renderer”. Sorry for wasting your time Stuart.t.