That means my arduino is connected to the dynamixel?? I tried to put my motor to move but it still can't move:(
"That means my arduino is connected to the dynamixel?"
This is important. You are using two different serial communication channels on the Arduino.
One is the regular serial UART, used to connect to your host computer via USB. That channel also uses pins 0 and 1, labeled RX, TX
That is initialized at 9600 baud in your setup. You also select speed 9600 on your PC. Prntln messages in your Arduino code also get sent on this channel and will appear in your console monitor.
You must use a second serial communication channel to control the Dynamixel. This channel will be using pins 2 & 3 and coded using the SoftwareSerial library and commands. It must be set to 57600, the default speed of the RX-28. The protocol is RS485 (not RS232), so this data needs to first go through the 485 driving chip, as indicated on page 13 of the RX-28 (Dynamixel). Thus it is Arduino pins 2 and 3, not 0 and 1, which get connected to the 485 chip.