Answer
Your instructor will teach them to you when you are ready. For an instructor to share these techniques with you requires a trust that you will not misuse them and hurt people inadvertently, nor teach them to others until you are properly trained and certified as both a Black Belt, and qualified Instructor.
Self defense is one of the primary reasons that people become involved in the martial art, and learning to defend yourself will be among the first things that your teacher should teach you. It requires the tutelage of a qualified instructor (check credentials to verify authentic knowledge of Taekwondo, and authorized organizational authority to teach). It cannot be learned adequately through reading, either online or in a book, and videos only show things without personal instruction. Sometimes an additional partner is needed to practice on while the instructor teaches and makes corrections.
It also requires a basic ability to move and use your body without losing balance and concentration. It is important to first warm up, and stretch to make the muscles, tendons, ligaments, and joints flexible. You first learn the basic components of each move, then practice them repeatedly with a partner until they flow smooth. At first, they should be done slowly for correct form, then gradually increase speed until it is fast enough to be effective in real life self defense. Initially the resistance of your training partner should be minimal until proficiency is gained, then intensified until it is as close to a realistic attack as safely possible without injuring your training partner. All of this must always be done under the close supervision of your instructor.
To enhance your self defense training after you have attained sufficient proficiency, you can train while wearing a variety of clothing as you would in your daily life, and practice indoors as well as out. Training carefully on a variety of terrain, with different obstacles to avoid, in various weather conditions, and against multiple attackers (unarmed and armed with safe training weapons) will prepare you for any encounter. Your choice of techniques and tactics should be altered according to the above conditions.
Proficiency at self defense skills requires a lot of practice of effective skills. Attending class more often will help to guide you better. However, it is important to understand that any real-life self defense situation can be potentially dangerous, or even deadly. No amount of self defense training will make you infallible, or bullet-proof. Part of self defense training is learning to avoid dangerous locations, people, and situations. It is safer and wiser to avoid a conflict by being alert to your surroundings, observe people and be able to read their attitudes and intentions, and to be a pleasant person who is not naturally aggressive, and does not provoke aggression from others. It is best to walk away (while remaining safe and alert), or talk your way out of a fight. Physical combat should ALWAYS be a last resort, and then it is applied only to the level necessary to protect the innocent, and neutralize a situation.