Or buy a typewriter, ya pansy!
You don’t need fancy software to write a script — any word processor will do. The thing to remember is that no matter how much you spend on software and learning curve time, you’re basically producing a document that’s supposed to look like it came out of a 1920’s typewriter.
I have met people who are sure they’ll write great scripts now that they have Such-And-So scriptwriting software.
It’s not hard at all to find script formatting guides. I pretty much do it each time I start a new script.