Transparent Background Using Brazil

Can someone explain to me how I can render an object and get a transparent background so that I can export it as a png file? This might be super simple but I am still learning. I am using Brazil and Rhino 5.

Not sure if its possible to do it it brazil but there is always another way! you can get the alpha channel from the render window then take it into photoshop- or by doing a simple render pass control In bottom of brazil properties - set background to white then render- this will keep all the material reflections from the environment but just make the background one simple solid white colour that you can take into photoshop and then turn into a png.

Not sure if this helps but doesnt seem anyone else has any ideas