I would read in each number into an array or vector, until the end of the data set. Do you know how to do that with fstream? I take it you covered it in class if you are asked to do it for homework? Are you familiar with arrays or vectors?
Then I would look at the data set. Only 1 is a positive integer that has no proper divisors, so first of all if n == 1, then output "none", otherwise, you need to enter a loop.
1 2 3 4 5 6 7 8
for(i = 1;i < n; ++n)
if(n % i == 0)
sum = sum + i; //Sum will become the total of the proper divisors of n.
Something like that. This loop can be optimized, but get it working first of all.