How To Increase Hours Of Employee At Given Index

Basically I need to increase the hours of an employee at the given index. Index is the position of the employee in the array, and amount is how many hours you will be increasing by.

This is what I have so far,

public void increaseHours(int index, double amount){
for(Employee e: employees){
if(e instanceof HourlyEmployee){
HourlyEmployee he = (HourlyEmployee)e
he.increaseHours(amount);
}
}
}
}

I'm not sure how to use the index to do this correctly, all it's doing right now is adding hours to every hourly employee