How do you enable windowed full-screen mode?

I never played LoL, but, according to a quick google search, there are two ways:

1. Run the game in windowed mode, set the resolution so that it matches exactly your desktop resolution, then hide the window borders using ShiftWindow.
2. Put BorderlessWindow=1 in your Config\gam‌​e.cfg and you should have no need for ShiftWindow. (source)

Again, I never played League of Legends, I just googled this information and have no idea if any of this will work.

The new location is C:\Riot Games\League of Legends\Config. Search there for the game.cfg file and change:

• Windowed from 0 to 1
• BorderlessWindow from 0 to 1