240 volt GCFI breakers come in two variants. Both kinds have two load connections and a white wire (usually coiled) coming out. The two load connections get wired to L1 and L2 on the pump, while the coiled white wire gets connected to neutral inside the panel. Some of them also have a third connection for load neutral. If yours has the load neutral connection you simply leave it unwired. In either case it is crucial that the coiled white wire coming out of the breaker get wired to the neutral bar inside the panel. In either case you also run a green ground wire from the panel ground bar to the pump. Sometimes the ground bar and neutral bar inside the panel are combined into one bar.