Along the right side of your screen (or at the bottom if you are on a phone or tablet), you have some TABS …. one of which is PEOPLE and here you can add FRIENDS.
The main reason for this is to see who is on line. My suggestion is you should add your PARTNERS and your DIRECTORS as FRIENDS. Doing this is the easy way to find them and can conveniently CHAT in PRIVATE way.
So when your friends are online, they are all listed for you and clicking on their BBO Name brings up the message box and you can chat away (see the message area below).