It does help other FOBC members when they play with and against one another if all members include within their profile a brief outline of your prefered system(s) and any conventions you like to play.  i.e. 1NT 12 - 14HCP, Transfers, 2NT 20 - 22 HCP, 2C strong etc.

Guide to updating your BBO profile

Guide to completing Convention cards on BBO

This is to show the opponents (and maybe a new partner) your conventions without having to ask. This is shown by putting your cursor on the name of the player and their profile is shown.

It is not correct etiquette to put a message to the table asking your partner what they mean by their bid.  You cannot send a private message to your partner, only to the Opponents. 

The blue box at the bottom has a number of options in ways you can chat with Table, Opponents, Club, Private.

Normally when playing in a Club, your partner would announce when you bid a convention. i.e. when you do Transfers, 2NT, 2C, this is completely different on BBO where you have to announce it yourself.  

You can do this when it is your turn to bid, by clicking on ALERT then put in your bid.  The Opponents will see a box appear with a red line around it, showing this is a conventions.  Your partner is not able to see this.