It is recommended that only a piercing professional do targus piercings. The targus is located very close to the inner ear and making a mistake could do serious damage to your ear. You must keep a targus piercing very clean.
A targus piercing is not only difficult, but also very painful. It's not the type of piercing that you can safely do yourself, and I suggest very strongly that you should not try it. You would be better off having it pierced by a professional in a sterile and controlled environment.
The safe way to get any piercing is to go to a professional who is trained in the proper piercing technique. Especially with cartilage piercings and piercings that are very close to your inner ear, an inexperienced person who is piercing themselves can cause excruciatingly painful damage to you ear that is usually irreversible.