You did not read your manual.
You did not search the forums.
If you had done both this post might not be here.
I will answer one question for you because you might not find the answer that you are looking for.
When you place stairs the stair segment starts on the floor that you place it on and ends on the floor above it.
I know you are new but you really need to read the manual which you can find in you FPS Creator\Docs folder in .pdf format.
The search button can be found at the top of the page and will take you to the search box at the bottom of the page.