How do I use code that isn't directly written out?

I have gone through the beginning tutorial on ROBLOX for scripting, yet I'm not sure how to do any other code with Lua that hasn't already been typed out. I have a game idea, but I can't make it without direct, typed-out scripts. I've seen other people's games, and they can somehow do that, but I don't even know where to start as to what to type in. Sorry if this seems like a bad question.. I'm pretty new to scripting!