It's a lengthy process, and I'm no teacher. I wouldn't even know how to learn it. All I can suggest is that you look at some existing scripts (preferably ones which you know what they do) and see if you can follow it through and understand what each line is for. Then try tweaking something and seeing what happens. The best way to learn is to do.
Hello Maruno, sorry to bug you but I was wondering if you could teach me how to script step by step?
I know it's an hard request so if you can't, I'll understand.
I assume you've made the event Autorun. Have a look at other events which autorun (such as the Poké Center nurse after you've fainted), and see how it turns itself off.