The team was waiting near the Boom Tube, waiting for someone to arrive. They were told they were getting a possible new member and needed to wait for them

Kid Flash: "How long are we supposed to wait for this person? Shouldn't they be here by now"

Nightwing: "Don't worry, it shouldn't be much longer. Be patient"

Not long after, the Boom Tube activates and announces the newcomer. Everyone looks at the Boom Tube expectantly