How to make a Sky? and second floor?

[Leonardo]

I've seen the video in youtube and eureka is great but, how i do open chambers or places without roofs?
how i do second floors?

[Arbars Zagadkin]

Hi. About your first question.

1. Create a large sector.
2. Make some in this sector (boxes, pool with water. etc.)
3. Use a F_SKY1 flat texture on ceiling in the large sector, and all sectors in the large sector too

For making a second floor you need use ZDoom features, for more - read ZDoom wiki.
I hope I helped you