What is Hypnotism? How do you hypnotize a person? What is the difference between Hypnosis Hypnotism?

Hypnotism is the art of putting yourself or another person into a relaxed state, basically getting the conscious mind out of the way, so that you can plant suggestions directly into the subconscious mind without the conscious filtering that is normally done in our fully awakened state.
Hypnosis and hypnotism are both nouns meaning the same thing. It is the art of bringing about the hypnotic state.
Learning to hypnotize a person is not difficult, but will require more effort than just reading a short answer here. Try the blog I've listed in the source box.