The obvious thing is that Simone is a feminine name because it ends with an e, so you would use "her" or "sa", but for the sake of learning...
The text, when translated to English, means "If I want to know the life of Simone De Beauvoir, I can read...". Sa biographie means "her biography". A biography is a novel written about someone else's life, so if you want to know about the life of Simone De Beauvoir, it'd be in your best interest to read that.
