Most fixtures only have one connector by default, e.g. a nozzle only has a single input connector and a pump has one output connector. Furthermore, some fixtures like valves have one input and one output connector. Once you need to connect e.g. two nozzles to a single pump, you would need a Distributor Fixture in between. A distributor is a virtual fixture, which automatically increments its input and outputs once a connection is established. To add a distributor right-click on the viewport and click on Add Distributor.
Following are three examples of how to use the Distributor:
Several Nozzles on a single Pump
Nozzles with Valves connected to one pump
Several nozzles powered by two pumps