I’ve exported my skybox in spacescape, When I open it in unity my skybox looks like a box. The lines don’t match up How can I make them line up? 
I had the same issue and in my case I noticed that only 2 of the images were not on their place. I had to put the image named “left” as a right texture and the image named “right” as a left texture and everything was ok then.
It is possible that spacescape exports the images the opposite way around from what Unity expects. Try flipping everything- put the top on the bottom, the left on the right and the back on the front.
Also, are you using a skybox here, or are you actually putting things on the inside of a box with a diffuse shader on it? By the looks of that screenshot, you are looking at it from the scene view, but you shouldn't be able to see skyboxes from there. Make sure that you are using the images correctly.