I am following the steps in this link: http://raptureinvenice.com/getting-started-with-mogenerator/
I have done this before in Xcode 4.6 but now that I have updated to Xcode 5 I couldn't follow it anymore.
I selected my target but I couldn't find the "Add Build Phase” then “Add Run Script”.
You have to use the tool bar.
Editor > Add build phase > Add run script build phase
Be sure that the target is selected, otherwise the option menu will be disabled.
Step by step with screenshots: http://www.runscriptbuildphase.com/