Qualifications
Many spend big bucks to go to film school at UCLA or USC or NYU, to learn how to write a script. Or you can go to an extension class, typically taught by a former screenwriter who sold a script once and now can tell you how you too can write and sell a script, and still end up flat broke without health insurance.
You can also read one of the myriad books on how to write a screenplay; or spend time the WGA script library reading scripts and figure it out yourself.