The document provides examples of using "have" and "has" in sentences based on whether the subject is singular or plural. It explains that "has" should be used when the subject is "he" or "she", or can be replaced by "he" or "she". It also explains that "have" should be used when the subject is "I", "you", "we", or "they", or can be replaced by "I", "you", "we", or "they". Examples are given to illustrate these rules.