This forum section is for the Arduino Yun Shield. You have the Dragino Yun Shield which is a competing product from another company. They are not the same, as there are some potentially important differences between the two.
Your best bet is to turn to Dragino for help. If you go to their wiki you will find a lot of support information. If you go to their product page, and select the Documents tab, there is a link for Hardware Source, where you will find the schematics.
Sorry, but I can't give any other advice - I have no experience with the Yun Shield: from Arduino, Dragino, or otherwise.