How does NSUserDefault works

first you need to grab the standard user defaults, then just set the integer for the key you want to save it as:

NSInteger highScore = 1000;
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setInteger:highScore forKey:@"highScore"];

that will save the high score to the standard user defaults.

If you want to read the high score from the defaults, just grab the defaults again and use the integerForKey method to retrieve the data using the same key you saved it under

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSInteger savedHighScore = [defaults integerForKey:@"highScore"];

its as simple as that.

generally its not a good idea to use NSUserDefaults to store data like high scores and what not, but its definitely the easiest way. NSCoding is a good way to save data like high scores and stuff. Here is a decent tutorial on how to use NSCoding