WANTED- Transparent BG output ?

Hi All,
I am weeding my way thru creating a smoke effect. Anyways on the output, I am getting a black background. I want a transparent background only. SO I can composite the smoke in a scene using PNG seq. I do believe I had RGB+Alpha selected for export / render. I sent the file over to After Effects to check the PNG and sure enough I am getting a black background on the PNG’s… Screen grab of the correct switch to click?

I found it here is a grab, due to me not knowing how to delete this thread. I will answer as to not waste time nor litter.