there are 3 ways to send a PM.

1) click on a members name - takes you to their profile page and then you can click on 'send a private message' which takes you to the PM section. The person to whom you are sending the pm to name appears under the 'Add Recipients' box in the "Recipients" section. This gives you a new pm to which you need to add a title and then type your message.

2) click on the 'Contact' icon under the members username/avatar in the panel to the right of their message. Then click on the blue 'contact' icon that appears. This will bring up the pm section with the message you are replying to shown in quotes in the message box and using the title of the original topic. You can either reply at the bottom of their message are delete it and just type your reply.

3) Click on the Private Message tab at the top of the page in the purple banner. Click on 'New Message'. Now you will have to "Add Recipient" - type the members username EXACTLY as it appears in any of their messages, then click on "Add". If you mistype their username it will tell you the user doesn't exist.

Options 1 & 2 are probably the easiest