How to change the User Interface of personal MIT App Inventor?

Hi friends,
I am Nick a computer science student and we are some friends working on create app inventor platform for our collage. can anyone tell me how to change user interface of MIT App Inventor ?

and one more question from my side how to add visible component some thing like button.

Thank You

The UI is mostly composed in Java, with some JavaScript, so if you aren't already familiar you may want to learn a bit of those languages first. The majority of the UI is constructed in appengine/.../ in the initializeUi method. The various components that make up the UI are spread throughout a number of different packages, such as boxes, explorer, editor, and widgets.

You should read through the How to Add a Component document, specifically section 4.