Function pointer stored in class

I want to be able to store a pointer of a function in a struct or class, then I can call upon that function when a button is pressed? here is what I have:

struct INFO
{
    std::function<int(int, int)> call_back;
};

class YO
{
public:
    YO() {};
    ~YO() {};

    int SUM(int A, int B) { return A + B; }
};

int main()
{
    //std::function<int(int, int)> datFunc = SUM;
    INFO info;
    YO* yo = new YO();
    info.call_back = yo->SUM;

    //std::function<int(int, int)> func =;
    std::cout << info.call_back(10, 10) << std::endl;

    system("pause");
    return 0;
}

I get errors:

Error   C3867   'YO::SUM': non-standard syntax; use '&' to create a pointer to member   FunctionPointertest 
Error   C2679   binary '=': no operator found which takes a right-hand operand of type 'overloaded-function' (or there is no acceptable conversion) FunctionPointertest