hi,
it is well described in the documentation here
https://docs.coronalabs.com/api/library/json/index.html
i am going to assume you are fresh at programming so here is the thing about corona sdk:
it comes with a well indexed and updated documentation that will solve 95% of all your issues.
it may seem daunting at first but the documentation is much better than code snippets off the web since it is not only updated but will also help you learn and understand the code better.
i say this from own experience doing exactly that.
now the good part. corona is powerful and will let you create almost anything, and because corona is well made, well documented and lua is both forgiving and straight forward, you will be able to do more and do it faster.
however, learning programming is like learning any foreign language, it takes study, practice and time.