You would first start by writing your message on a piece of paper, then you would place it into a sealed envelope, after you put a stamp and address on it.
종이에 메시지를 쓴 다음에 봉투에 넣어서 붙이고 그걸 가지고 주소를 쓰고 우표를 붙여서 보내는 겁니다.