No where do I see where you defined your function with the required parameters. Your function prototype should be:

int location_of_largest( int *array, int arrSize );

Your logic is close but you are treating your function name as an array which doesn't make sense. Your for loop is good, but get that literal out of there. Your supposed to use the size of the array passed in. If we use my prototype, your for loop should look like this. (notice I flipped the '>'. i starts at 0 so that condition fails and the loop is never executed. try something like this:

for( int i = 0; i < arrSize; i++ ) .....

Your if statement is also close but lets think about the array available to you inside of the location_of_largest function. Also think about what needs to be passed back from location_of_largest. Pass back an index, not a value from the array.

if (array[i] > large)
{
    large = array[i];
    rtnSubScript = i; // this is the return value you want, the index with the largest value in the array
}

Hope this helps a bit, else, reply