What do I have to do to bring a class action lawsuit against a public company that I invested in?

I don’t want to say the company specifically but it is listed on the pink sheets. It kept going down and I kept dumping more and more money into it on positive news from the CEO. However, the CEO failed to live up to his end of the bargain on many different occasions. Eventually the company had a reverse split and know my $2,000 investment is worth about $5.00. What do I have to prove to win the case? Message boards have insisted that the whole company is a scheme! Any advice?