Well, I have no idea about the legendary pokers, but I can help you with the PMs.
Click on the name of the person you wish to send a PM to. A drop down menu should appear. Click on the option "Send a PM to..." A new screen should come up that looks like the reply/new thread screen. Fill out your message, enter a title for the PM, and click on the button on the bottom of "Send Message."
To look at your new PMs: If you look at the top of the screen, there is a small box in the right-hand corner that says
"Welcome, ...
You last visited...
Private Messages: Unread 0, Total 0"
If you have a PM, the Unread number will be 1 or higher, depending on the amount of PMs. Click on the "Private Messages" link in that box, and a new screen will come up. It will be a list of your new PMs. Click on the titles of them to read them.
Anyy questions, just ask in here, but it's pretty simple.