So, I hope this Instructable will help you on your quest of learning how to thread eyebrows....
-Then tie the thread in a knot to make a loop.
-Twist the fingers on one hand to make an 'X'.
-Twist your fingers a few more times in the same direction (about 4 twists should be enough).
-Keep the fingers of one hand pinched together while you open the fingers of the other hand. This will slide the twisted part of the thread over. This movement is how the thread grips the hair and pulls it out. (kind of like when you rub a rubber band over your arm and it pulls out your hair...actually it hurts like that too when you are removing multiple hairs such as your upper lip).