You use himself to refer to a man, boy, or male animal.
He poured himself a whisky and sat down in the chair.
他给自己倒了一杯威士忌,然后坐在椅子里。
William went away muttering to himself.
威廉喃喃自语地走了。
In written English, himself is sometimes used to refer to a person without saying whether that person is a man or a woman. Some people dislike this use and prefer to use 'himself or herself' or 'themselves'.
There is nothing more dangerous than someone who thinks of himself as a victim.
没有比自认为是受害者的人更危险的了。
You use himself to emphasize the person or thing that you are referring to. Himself is sometimes used instead of 'him' as the object of a verb or preposition.
The president himself is on a visit to Beijing.
总统本人正在北京访问。