nawaneeth,
if you don't know ladder programming, then you surely don't know much about PLC's. Ladder programming is what PLC's initially were made for. The first PLC's were designed to replace relay logic. Ladder programming is directly derived from drawing relay logic circuits (the American way, that is). The best place to start learning ladder is right on top of this page. Simply click on the "LEARN PLCS" text and take it from there. Another resource is the help button in the software you're using to program the PLC.
Kind regards,