How do i send a message to a specific person?
You can just click on their picture and it will bring you to their profile page. Then you can type in their message box.
As claimed prior, any messages are viewable by all, but to clear it up, use the "at" symbol and their title name followed by your message. This should allow it to pop up in their notice when they log in next. ( Example @A MyEpilepsyTeam Member )
Just click on their name and type in the box that says "Say Hi To...."