There are three ways you can send a message. Indicate your name and your instructor's name. When discussing an issue always be prepared to provide evidence to support your views. For example, cite a textbook, course reading, or lecture to substantiate your assertions. Feel free to ask questions.
Good discussion begins with questions.
Wonder aloud about either issues covered in class or about how something beyond our class ties in with a class topic. Address others as you would wish to be addressed. The moderator reads it to make sure everything's appropriate, then forwards it on to the entire list. It's that simple. I'll be back shortly to suggest some opening topics for discussion.