You should use himself in most contexts, since it is the correct version of this word. Hisself is considered a substandard dialectical variant.

Is there such a word as himself?

Himself is a pronoun. It refers back to the subject of a sentence or clause, when that subject is a male person or animal. It can be used reflexively (he gave himself a tattoo), or for emphasis (he himself should ring the bell). It can also be used in absolute constructions.

Do you say himself or themselves?

You use themselves instead of 'himself or herself' to emphasize the person you are referring to without saying whether it is a man or a woman. Themselves is also sometimes used as the object of a verb or preposition.