Yes. The mail icon in the upper right will show a number of messages in your Inbox (if there are unread message in your Inbox). Click on this icon to view your messages and see the four tabs:
You may send a PM to any user within our terms. If you are a fan of users, their usernames will automatically show in a drop-down menu on your Compose tab. If you want to send a PM to another user, go to the user's profile page and click "Send a private message" next to the message icon.
If you are already a fan of the user: