As noted, click on the avatar of the person you want to converse with. There's a link in the window that opens "Start a new conversation". Also, if you hover over "Inbox" on the upper right (hover, not click) you'll see "Start a new conversation link on the lower right of the pull down menu. Well, actually you can click on "Inbox" and "Start a new conversation is there on the upper right side, also.I have eleven posts and I still can not pm. I have went to inbox but I don't see where it says start a conversation.