- Download the .zip archive and extract it. What you need is the .swc file in the lib folder.
- In Flex Builder / Flash Builder, go to your project’s properties, and then to the Flex Build Path panel.
- Click on Add SWC, and select the as3corelib.swc file
- In your project, add the following line: import com.adobe.serialization.json.JSON;
Adobe itself made a JSON library that you can find at https://github.com/mikechambers/as3corelib Follow these steps to add your JSON library to your Flex project: