The ISS currently has a crew of 3, that was brought there on Expedition 63 by Soyuz MS-15.

Crew dragon demo-2 will fly with Victor Glover, Mike Hopkins, Shannon Walker and Soichi Noguchi, and subsequent flights will also bring 4 astronauts, which means that the ISS will have a crew of 7 on board at once.

However, the ISS only has 6 permanent 'beds' (2 in the Russian side and 4 in the Harmony module of the NASA segment).

Where will the seventh astronaut sleep? Will they strap their sleeping bag to a wall? Will they implement shifts and sleep while another astronaut is awake?

Will the odd one always be the same person or will they take turns sleeping outside of the crew cabins?