You can’t export the project to others platforms in the sense of just clicking a button and it will be ready to deploy to iOs, Android, Bada, and so on.
1 - Make a backup of your project. Better safe than sorry.
2 - You must use the scripts provided by cocos2d-x in order to create projects for iOs, Android, Bada, Blackberry Playbook (you chose for which platforms you want to deploy your game). Please refer to Chapter 1 - How to Create a New cocos2d-x project on multi-platforms
3 - You reuse the common source code in the other projects (your code) but you may need to adapt it for each platform if you wish to use some platform specific features (for instance, Game Center on iPhone and AdMob on Android).