If your MySensors gateway is USB, select as follows,
Tx message processing delay: Transmission delay between on each message from MyController to this gateway to avoid the collision on MySensors network.
Driver: Keep it as Auto
Port name: default /dev/ttyUSB0
Baud rate: default 115200
Retry frequency: For some reason, if your gateway goes down. MyController attempt to reconnect every X seconds once.
Now you can see your gateway and nodes on MyController.