Perhaps if you'd posted your actual requirements at the start, we could have saved a day of dribbling information.

> I have been stuck and dont even know where to begin.
I gave you a start, but you're just a rabbit stuck in the headlights of the whole problem.

Stop staring at the whole thing and panicking, and focus on doing small things one at a time, and build up step by step.

* This function prompts the user with the string pointed to by prompt
* and then reads a single character from the keyboard, and throws the
* rest of the input line away. It then checks if the input character is a
* lower case letter, in which case it upcases it. It then checks if
* the resulting character is one of the N approved characters given
* in the N-length character array pointed to by L. If the character
* is not allowed, the routine prints a list of allowed characters, and
* then repeats the whole process until an allowed character is entered

Given your other posts, it looks like you need
Code:
int getCharInSet ( char *prompt, int N, char *L ) {
    return 'a';
}

int main ( ) {
    char allowed[] = "abc";
    int ch = getCharInSet("Type a char",3,allowed);
    printf("You entered %c\n", ch);
}
The object is to take each coloured requirement IN TURN and add it to the program.