A private message is similar to an email. You can send and receive messages from anyone on the Forum without exchanging any personal information.
If someone sends you a private message, two things will happen.
1) You will get an email in the email address you entered when you set up your forum account. The email will contain the complete content of the message. If you would like to reply back to the person, you can log into the forum and reply back.
2) The envelop by your screen name at the top right side of the forum will turn from gray to blue.
Just click on the envelop to access your inbox where you can read and send messages.