1. use mozilla firefox Browser
2. open your facebook then open your Dragon City
3. put your mouse pointer in upper left side then right click it. or just right click that RED CIRCLE that you see in the photo.
4.then you can see this
5.Go to This Frame then click View Frame Source
6. Then this code/source will appear.
7. Then click Ctrl + F (in your keyboard)
OR click Right Click (mouse) then click Find Again
8. then type in the search box the word " session " then you can see your session id number..
Sorry my english is not good but i hope i can help you in the easy way ..
SOON to how do this in google chrome