Everybody does this mitzvah (commandment) of semichah, which is leaning on the korban (offering) that you're about to offer, except for a deaf-mute, a person who doesn't have knowledge, and a minor. All these people don't have the necessary knowledge to do the action of semichah. Other exceptions are a blind person, as we learn now from a pasuk (verse), and also a non-Jew. A shaliach, an agent, and a woman are also exceptions. None of these do semichah.
Semichah is considered to be a secondary component of bringing the korban. The avodah (Temple service) is valid even without semichah. The mitzvah of semichah is done by leaning on the head of the animal with two hands, and the animal is slaughtered in the place where they do the semichah. Semichah has to be done in the place where the korban is slaughtered, which is in the courtyard of the Mishkan or the Beit HaMikdash. Right after the semichah is done, the slaughter is also done.