For some types of bookings, you may need several employees or one employee and one room. To add multiple resources (rooms, employees, equipment, etc.) to a single booking, you can either predefine them as a service, or create them manually.
You can find out how to create a service with predefined dependencies for several resources here: Create dependencies between multiple resources
Of course you can also add one or more resources when creating a new appointment. Click on an empty space in your calendar and create a new appointment. In the resources area of the appointment window you can then for example add more employees. Either select the corresponding resource in the drop-down menu or use the search function in the field by typing in the name of the resource.
The appointment is then created for all selected resources. This way you can for example manage team meetings easily.