error in implementationg enum in c++ inside class

As always in C++ you need to declare something before you use it. You must therefore move the definition of enum Suit before the declaration of the suit member.

You need to move the enum definitions before the point you use them. For instance something like:

#include<string>
using namespace std;
class Card {

public: 
    enum Suit {Clubs, Diamonds, Hearts, Spades, UNKNOWN_SUIT};
    enum  CardName {Ace, Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Jack, Queen, King, UNKNOWN_CARDNAME};
private:
       Card::Suit suit;
       Card::CardName cardName;
public:
    class NotInitalised : public exception{};
    Card ();
    Card (int card);
    Card (Card::Suit s, Card::CardName n);
    void setCard(Card::Suit, Card::CardName);
    Card::Suit getSuit();
    Card::CardName getCardName();
    Card::CardName getCardName(int);
    int getCardValue();
    string toString();
};

should work.

Also you don't need to qualify the uses of the enums inside your class definition, i.e. instead of

Card::Suit suit;

you can use

Suit suit;

I usually declare all the public elements of a class before the private ones, since I want to have the public interface of the class when I look at it, but this is just a style preference that others may not agree with.

Remove scope resolution operator and move type declaration before use of that type

You class will look like as follows:

using namespace std;
class Card {

private:
    enum Suit {Clubs, Diamonds, Hearts, Spades, UNKNOWN_SUIT};
    enum  CardName {Ace, Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Jack, Queen, King, UNKNOWN_CARDNAME};

     Suit suit;
     CardName cardName;
public:
    class NotInitalised : public exception{};
    Card ();
    Card (int card);
    Card (Suit s, CardName n);
    void setCard(Suit, CardName);
    Suit getSuit();
    CardName getCardName();
    CardName getCardName(int);
    int getCardValue();
    string toString();
};