C++ copy constructor for class with dynamically allocated array

Just starting on C++ (a few days now), I come with C background.

I have a class that holds, mainly, an a pointer to an int array with the following code:

class Array
{

private:
    int * _arr;
    int _size;
public:
    Array();
    Array(int size);
    Array(const Array& obj);  // copy constructor
    ~Array();
    void readInValues();
    void mult(int num);

    void add(int num);
    void printArray();
};

_arr is a pointer to an int array, when creating a new instance using the copy constructor I would to create a new int array on the heap (I think). In the copy constructor:

Array::Array( const Array & obj )
{
    _arr = new int[_size];


    for(int i=0;i<_size;i++)
        *_arr[i] = *obj._arr[i];
}

The 1st thing I do is allocate memory for the new array (_size is a primitive type so being copied automatically as far as I understood). The next thing I would like to do is copy the array itself using a loop. This parts fails the compilation saying illegal indirection. I am not sure why...