If you don't already have a partner lined up for any particular event you can use one of two options.

1) You can add your name to the "Partnership Desk", which is essentially a holding area for single players. To do this you log on to BBO and find the event you wish to play in, as normal. Click on the event, but instead of inviting a partner to play, click on "Partnership Desk", which can be found at the top of the screen. Then click where it says either, "I will pay for only myself" or "Partner must pay for me". Your BBO name will then be added to a list. Now, if and when another single player comes along, they can look at the Partnership Desk list, and have the option to invite you to be their partner for that particular event. You can either accept or decline the invitation. Both players must be online at the same time. You will not be charged the entry fee unless you successfully locate a partner. If you aren't successful, the TD may still be able to invite you to play once the event starts, but only when the event has an odd number of pairs, i.e. where there would normally be a sit out. Your partner then, may well be a Robot.

2) You can enter the event with a Robot partner. Again log on as normal, and select the event you wish to play in. Click where it says "Play with a Robot (Extra 0.25 BB$). You are then registered to play. 

There are also various whatsapp groups which members utilise to find a partner. These groups however, are essentially private, and are not administered or sanctioned by MRBC due to GDPR reasons.