It seems that the directory for the iOS Simulator has changed. It used to be in ~/Library/Application\\ Support/iPhone\\ Simulator/
and now it\'s in ~/Lib
According to charles documentation
The iOS Simulator should use the system proxy settings. If it doesn't, please try quitting and restarting the iOS Simulator. As of Xcode 6 it appears to be important that Charles is running and set as the Mac OS X system proxy before you run the iOS Simulator.
Read Here
So just quit your simulator, open charles and then run the app again. After that you can track your network calls.
NOTE: Your network calls will fail if you quit Charles. So you will need to either quit the simulator and run it again or open Charles again.