Here is the correct placement for the words:
The central idea is the most important idea in a text. Authors use details to support the central idea. The topic is the general subject of a text, and the text structure is the way in which the text is organized.
So the arranged text is:
The central idea is the most important idea in a text. Authors use details to support the central idea. The topic is the general subject of a text, and the text structure is the way in which the text is organized.