Hi, there is seldom a thing like a simple app as simplicity on screen may still require a lot of code under the hood.
That being said, the best way to learn Corona SDK and Lua is to try the documentation and tutorials which are available both online and in a demo folder once you install it.
You will need a text editor, form which there are several, so again, look at the website and the category 3rd party tools.
I am personally using the sublime editor.
It may at first seem like much and it is, but keep hammering and studying and slowly the puzzle pieces and the logic will fall in place, and you will be on your way to become a developer with both skill, passion and dedication.
Good luck and welcome to an alternate reality 
P.S I just started myself last autumn and am working on my 3rd app.