Step-by-step explanation:
I could not find the rest of the question but I will try to help you by explaining how can you find the main idea in some paragraphs.
The main idea of some passage or paragraph is considering what the passage\ paragraph is about. You can find it by reading the text couple of times and see what the text is describing and explaining to you.
When you find what the text is about, you will know what is the main idea of it.