Hi Toheart89,
Once you have successfully applied for relief teaching, you will
have to wait for the school to contact you when they are in need of
relief teachers. Sometimes you may not even get called up at all
after a few months, as there are plentiful of relief teachers
around.
Teaching in a kindergarten will not really give you any sort of
advantage in entering NIE, unless the principal writes a special
appraisal for you to show that you have the potential to teach
children of higher education levels.
Cheers.