On "S" screen you need to change method of arming missile warhead (black switch in right down - to right) so warhead is activated by command from your station. Then you need to manually control expected range of the target by manually managing elevation through known altitude from board.

It requires big precision and you also need to adjust manual setting according to the target flight direction - if it is flying towards you, lengthwise or receding.

It is like Volkhov's I87V-three-point but done manually.

As I said it is not easy but I do not know about easier method.