When you summarize, you explain the main idea(s).
You must read a passage closely, finding the main ideas and supporting ideas. Then you must briefly write down those ideas in a few sentences or a paragraph. It is important to understand the difference between a summary and a paraphrase. A paraphrase is simply a rewriting of a passage in your own words.
The steps are:
(1) read and understand
(2) find the keywords
(3) write short sentences with these keywords.
Hope this helps