Hi i have some experience in javascript. 

I am trying to customize the authoring tool for my client. i need to change the text on some of the buttons. like for example, the text on "Add article", "Add block" etc. 

In the source code i found that the text comes from the en-application.json file. But i tried changing that but it did not reflect in the authoring tool. 

also i would like to change the css. Can some one guide me where i can do that ?

I am using vagrant to start the authoring tool.