click on the member's board name that you want to send a message to, and a box pops up with the option to "send private message", click on that. A text pop pops up addressed to that member, and a text box to type your message. When you're done composing the message, click "submit" at the bottom of that box. If done correctly, you will the sent message in your sent folder. you may experiment with one to me if you'd like.