// get this section
ConfigurationSection mySection = arenaSection.getConfigurationSection(adminCommand);
// enable section
mySection.set("enabled", true);
// create section with location stuff - selected blocks
mySection.createSection("a", LocationHelper.getXYZLocation(new Location(world, minP.getX(), minP.getY(), minP.getZ())));
mySection.createSection("b", LocationHelper.getXYZLocation(new Location(world, maxP.getX(), maxP.getY(), maxP.getZ())));
// save config to file
SimpleSpleef.getPlugin().saveConfig();