How to reverse engineer an application or decompile it

Question

I need help

Answer 1

You are asking this in what context? Is it software development or something else?

Answer 2

Software engineering

Answer 3

I have just stepped into the IT field and from what I know is reverse engineering is usually done to either replicate or enhance a software application.

I'm not sure but the Agile model for software development let's you do that.