Click a cargo in the Cargoes module list.
When the drawer opens, open the action menuin the top right.
Click the Allocate Cargo button to open a dialogue for allocation.
The allocation dialogue is a three-step process. Once you have selected a vessel, a list of all the voyages on the vessel will appear. Sort and filter the list to find the exact voyage you want, select it, and a preview of the voyage schedule will appear, with cargo ports on the left, and port calls on the right. The scheduler will attempt to link the existing port calls on the voyage with the cargo's cargo ports. If no port call exists, a new one will be created at the end of the voyage. These are denoted by a blue "NEW" chip. You can re-arrange the port calls by dragging and dropping.
When allocating, the cargo will also have its company and business unit changed to the voyage's company and business unit. You can edit the cargo's company and/or business unit after the allocating if you want it to be different from the voyage's.
Click Allocate to allocate the cargo and create any new necessary port calls on the voyage.