BBO uses a self-alerting system similar to high-level tournaments where screens are being used. That is to say you alert and explain (if asked) your own bids.
When you are about to make a conventional bid click the Alert button before selecting your bid and type in the explanation (not the name of the convention) . It will show grayed only to your opponents and they can click on it to read what it means.
In case you forgot to alert, you can, at any time, click on f your bid and explain it.
In the same manner you can click on an opponent's bid (alerted or not) and require an explanation.
