Hmmmm....I don't think you can technically "respond" to a private message. You can go to the person's profile page and leave them a public message, or check the box and it will be sent as a private message.
lablover, when you go into your message board, which is found when you click on your screen name or the large letter L at the top right of the screen, and you see a message to you.... to answer, just click on that person's screen name, up will pop a section where you can send them a message.
If you wish the message to be "private", at the top right of the message box is a place where you can click. You can also add hugs if you wish, hugs at the bottom left of the message box. Then just click on "send message" or whatever it is called, which is at the bottom right of the message box.
If you wish the message to be "private", at the top right of the message box is a place where you can click. You can also add hugs if you wish, hugs at the bottom left of the message box. Then just click on "send message" or whatever it is called, which is at the bottom right of the message box.
Hope this helps :)