The diagram shows a three-move tsume(checkmate) problem. It's your turn. You have a Rook in hand. Please think about where is the best square to drop your Rook to checkmate the King as the first move. The answer will be found in the comment.
It's recommendable to replay the answer line using your own shogi board and pieces. If you do not have them, the following pages might be of help;
Please refer to the article about the shogi notation in Wikipedia, if necessary linked below.