It depends whether you wish to manipulate the JSON on the client or server-side.
If you want to access the values in
Java code you will need to download the json-lib.jar from
json.org and add it to you're classpath.There is documentation on the site to assist you.You can give you're jsonString to the constructor of the JSONArray class and then use it's retrieval methods to access the values.
If you want to access the values in client-side javascript you can see examples of how to do it in plain javascript here :
parsing JSON in javascript