For running a simple code with Xcode after running Xcode choose “Create a new XCode project”. (You can also go to “File|New|New Project...” or press Shift-⌘-N). This will bring up a screen in that screen select "Application"then select "Command Line Tool" and then click next .Now enter a name for your project and select type c++ and click next in upcoming screen select a directory for you project and click "create" now you can write codes in main.cpp file in the left panel for running your code just click on "Run" button .
Update:
In Build options click "Build settings" and then click "All" from "C++ language Dialect"and "C++ standard library"tab you can choose the compiler and c++ standard that you want included c++11.