'himself' can be a reflexive, intensive, or recursive pronoun.
As a reflexive pronoun, it refers back to the subject or antecedent of the sentence, to add emphasis on them. For example, 'Bob cooked the meal himself.' Here, 'himself' emphasizes that Bob cooked the meal personally, and no one else. As an intensive pronoun, 'himself' can be used to emphasize an attribute of the subject, used when the speaker wants to add emphasis, and is most often used in rhetorical questions. For example, ' he himself was the one who made the mistake.' Here, 'himself' is added for emphasis, and to add a sense of surprise, making the sentence into a rhetorical question. As a recursive pronoun, 'himself' can be used when referring to something that was previously mentioned, or that has already been established. For example, 'He walked into the room himself.' Here, the speaker is referring back to an earlier statement of something the person had done.
1.He taught himself to read when he was just three years old.
2. She criticized herself for not achieving more.
3. He himself designed the project.
When using 'himself' as a reflexive or intensive pronoun, it should be used in conjunction with a pronoun or noun that it is referring back to. When using it as a recursive pronoun, be sure that you have already established the antecedent the pronoun is referring back to in the sentence.