There is already a thread upon this matter, of which you've asked this question in as well. I'm sure you already know where it is, but here's the link anyway:
http://www.pesgaming.com/showthread.php?t=91007&page=15
[MENTION=218089]Akdas Farid[/MENTION] - When you begin a Master League, you go through multiple option screens. It is these option screens in which you choose the 'settings' for your Master League. Some of these settings include difficulty, match time, frequency of transfers (of which you can turn off), as well as player development (which you can also turn off).
League Mode was very similar to that of the Master League, with the only major differences being that normal League Mode would not allow any transfers or player development, whilst also being just a 1 division campaign I believe. Now, in PES 2013, you can essentially recreate League Mode by using the ML options available, and you will ultimately have a 2 division League Mode, as you start further down the pecking order within the ML.
Simply put, begin a Master League, and the first screen that will appear is a "General Settings" screen, in which you choose the settings you want. So if you want to recreate a plain League Mode, just turn off player development and market activity (transfers).
