Hi @IanHsueh
You can refer to the examples in the RTD. They are the same as shown in this training presentation: S32K3XX COMMUNICATION MODULES: FLEXCAN WITH RTD AND LOW-LEVEL DRIVERS.
These projects are configured for loopback, so you will need to enable normal/user mode and initialize the transceiver output pins (CAN_H & CAN_L).
There are also some community posts with examples:
Best regards,
Julián