how to make the effect cc particle world transparent

Hi community!
I would like to use the cc particle world effect in one of my compositions. But when I use it I can't see my composition in the background anymore and I can't find any option to change that in the effect menu itself. Maybe I need to create a transparent layer and apply the effect to it but I don't know how to do that aswell.

It's probably a simple problem but I don't know how to find the solution. 

instead of the black background I want to see the composition underneath it.

Any help is appreciated thanks!