Becoming an editor is not difficult.
Write a complete and honest application and show us that you understand the guidelines by writing decent tiltles and descriptions for 3 websites that fit in the category you are applying for (those websites should ofcourse not be listed yet).
Being rejected is no shame, many of our current editors had to try more than once. Each rejection email will have tips about how to improve. Those tips might be in the form of a standard mail or in the form of personal comment (or a combination). Read them, read the guidelines and try again.