How do you set BP_Skybox opacity?

Greetings!
I’m strugglign with this rather simple concept;
What I’m trying to achieve is an sky with a bit of galaxy/stars in the background, so I bought SpaceBox Dim in Blueprints - UE Marketplace

I have:

https://forums.unrealengine.com/attachment.php?attachmentid=119249&d=1480322911

and

https://forums.unrealengine.com/attachment.php?attachmentid=119248&d=1480322896

What I’m trying to get:

https://forums.unrealengine.com/attachment.php?attachmentid=119250&d=1480322934

(Photoshoped together)
Basically I just need the sky to be a lil bit more transparent to show the huge space box in the background while maintaining the suns and cloud effect.
what should I do to achieve such effect?
thank you very much in advance.