You would first start by writing your message on a piece of paper, then you would place it into a sealed envelope, and from there, you would go ahead and send it after you put a stamp and address on it.
你首先将信息写在一张纸上， 然后把纸放入信封，封上信封， 写上地址，贴上邮票， 然后把这封信寄出去。