Just take the problems one by one.

1. Declare a single dimensioned array of type integer that can have up to 50 elements.

Do you know how to declare normal variable like:
int x;
double y;
If you do declaring arrays shouldn't be a big problem, it's done like this:
DataType NameOfArray[NumberOfElements]
for example:
int x[10];
is it clear now...
And I think if you are using a C++ book it should be there just go and check it out.
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2. Input values, one at a time into the array from the data file, until there are no more values to read, keeping a count as you go.

first you should know how to access each element in the array and it's like this:
if you have a five-element-array int array[5];

The elements will be:
array[0]
array[1]
array[2]
array[3]
array[4]
So you access any of them.
In order to input values one at a time, you have to make a loop that repleated n times where n is the number of elements and each time input one element...
I'll not write the code for you, you should try, if you couldn't I will give you more help.

So try to solve thte first two part's and them we can deal with the rest, but you should work on it!

Post you work and then we can continue.