To paraphrase means to take a text and rewrite the text in your own words. You cite a certain number of words in the follow-up to your question. If you are being required in an assignment to paraphrase an article, that means your professor wants you to read the article, comprehend it, and put it into meaningful language for yourself. A paraphrase is about the same length as the article. So look for an article that is about a page, single-spaced.
If you were to summarize, you would look at the article and make it smaller.
The purpose of paraphrasing is to help you look at a difficult text that needs disecting. As you put it into words that make more sense to you, you are more likely to remember and internalize the information.