In any topic or conversation you have the choice to 'reply to conversation' or 'reply to topic' (depending on where you are inside the community) as depicted below.
- Reply to Conversation - usually means you are in the private message system.
- Reply to Topic - usually means you are in the general public forums.
[Image below is of a general public topic.]
[Image below is of a private message]
Clicking to reply will open the editor for you to type your responses as depicted below.
- Type Response.
- Click "Submit Reply"
See your reply and wait for other people to reply back.