Form client scripting

Can someone help me telling me why I can’t see doctype folder if I already create 4 doctype, I want to create ter library_transaction.js but I can’t find the folder to create that file

Are you on a development environment?

I’m starting to work with this, so I’m following the tutorial

To receive help, you need to define the environment. Which tutorial are you following?
If you are in a development environment, you need to start the bench from a console. On another console you can execute other bench events.
If you are creating a custom app, you should create the directory structure, install the app to the bench and make customizations using the Administrator user and the Developer options on your application.
I’m following that tutorial i’m starting the bench from a console