How can I find out whether or not I qualify to join an ongoing nationwide wrongful termination case against a company?

I recently discovered there is an ongoing wrongful termination case against Sam's Club/ Walmart. I feel I was terminated wrongfully three years ago and was wondering if it wasn't too late to try and get involved. The reason they gave me as to why I was being terminated was that I broke the law by not allowing the company to pay me overtime. What they were referring to was the fact that I manually clocked myself out so as to not exceed 40 hours. The company was very stern about associates working over their scheduled fulltime hours and that evening I had stayed to help a member in the photo lab department and went past my 40 hrs by about 20-30 minutes. The reason I had manually clocked myself out was to keep myself from being written up for going over my 40 hrs...big mistake.