Problem about Exercise 3.2

I have already writed a here. And according the folie excuted the command rosservice call /move_bb8_in_square.but generated a Error like that

Hi @weizhenyu1556,
are you running the service in Terminal #2? It has to be running in order for you to be able to call it.

have no ideal about how could I running it,jue in this window

Read the instructions carefully. You have to execute your script with rosrun or roslaunch.