How do I castle?
Move the King two squares towards the Rook.
Above, the "short castle" (castle with the King's Rook) is shown. There is another castle move, the "long castle", which involves the Queen's Rook. In the long castle move, the King also moves by two squares (and the Rook travels a little bit more).
If the castle move is legal, the Rook will also move.
The position after the short castle is shown above.
Please read carefully the rules, they explain when a castle move is possible and when it is not.
If CHESS refuses your castle move, then you can be certain that it is not legal at the moment you play it. The rules will tell you why.
The idea is that castling is only allowed as a quiet development move in a quiet position.