To play on BCL you have to have a paid subscription but once you subscribe all games are free. To see the different subscriptions available go to: https://www.bridgeclublive.com/Members/price-list-NL.asp
On BCL you can just play games with random other members in the Social Room or you can play more competively in a DIDO (Drop In Drop Out) tournament (see : https://www.bridgeclublive.com/BCL_DidoTourney.asp ) in the Daily MPS room. There are also regular competitions organised by the EBU. For some of the tournaments on BCL you can earn Masterpoints.
You can also play with a pre aranged partner against two random BCL members or as a pre arranged foursome. The instructions for playing a private game of four can be found via this link: A-Private-Table-for-4-
Other useful features include the Teams of Four room and the Coaching Corner (also seperately described)
To get the hang of how things work you can spectate first. Chose a room other than the lobby, click on that room and a list of tables appears Click on the blue eye symbol next to the table number of your choice and click on one of the N,E, S or W players . You can then watch the four players at the table.
NOTE: If you want to play by partnering another random BCL member you want to make sure that they are playing a compatible system as a number of overseas player will be playing Standard American Yellow Card (SAYC) where they play 5 Card Majors and a Strong NT (or some other system). The best way to avoid this is to look for someone already sitting at a table waiting for a partner and click on their alias. This will show you their profile and the system they are playing.