At the top left of each post is the person's USERNAME. Just left click on that and a small drop down menu should appear. One of the options is to send a private message.
Also, at the top right of the entire screen, you can see a link under your username that says Private Messages. If you click that, it will bring you to an inbox looking screen...in the left column are options to Send Messages...when you click that, you can type your message and enter who you want to send it to towards the top of the message body...will look like a E-mail.
Also, at the top right of the entire screen, you can see a link under your username that says Private Messages. If you click that, it will bring you to an inbox looking screen...in the left column are options to Send Messages...when you click that, you can type your message and enter who you want to send it to towards the top of the message body...will look like a E-mail.