@bielen - there will be two C(ommon) terminals on the Rachio to put the two wires from the COM port. There will be a M terminal to put PM/V wire - be sure to enable Pump Start Relay/Master Valve option in the Rachio app to make that port active.
For the SEN port - is that a rain sensor or what type of sensor is it? You don’t have to use a rain sensor, but you can with the Rachio with the S1 and -24 terminals.