How do I use the shadow behavior

I tryed to add some shadows to my characters and this is what i managed to do.

So basicaly there is a circle with the Shadow Caster behaviour and a source of light. How do i change the shadow opacity? I read the manual (https://www.scirra.com/manual/177/shadow-caster) but i couldn't found how to do this.

One way to work around opacity is to cast all shadows on a specific layer and then change that layer's opacity.

And can i do it without changing the object obacity too? (so only the shadow change the opacity)

Change the opacity of ShadowLight object itself.

shinkan thank you, it worked