Get a better view of the LED lights
If you get a better view of the wifi board, there are three LED lights. As the above-mentioned, if the insertion direction is right on the wifi board, the three LED lights would be lightened, as shown in Figure 2-4, where LED1 is the indicator for the power source, if the LED is light with red all the time, it shows that the power source works normally; LED2 is lighting with green, which shows the wifi module works normally; vice versa, the wifi module cannot work normally if LED2 is dark. LED3 is denoted by the state of wireless transmission. If LED3 is shining fast, it shows that the wifi module is transmitting data, and shining slowly shows that the wifi module is idle and has no data to transmit. Moreover, if LED3 is dark, it shows the wifi module close the wireless transmission.
Note that, if the wifi module has ever been used (i.e., it is not a new wifi module). To ensure the configuration is right, the wifi board should recovery the factory default setting. If wifi board is already default setting, you can skip over this step. Firstly, give the wifi board a 5V (350mA) power and wait about 30 seconds. Then press the RST button on the Arduino shield board for about 6s, as shown in Figure 2-5. The wifi board would reboot. After this, the wifi board can return to the default factory setting.
Fgure 2-5 RST button on the Arduino shield board