Collect enough arrows to defeat the dragon use arrow keys to move. The levels will get harder as the game goes on. Their are only five levels if can't find arrows, look on the left side. If having technical difficulty such as you can't see the arrow click the flag again.
Thanks to https://lawrencemann.co.uk/portfolio_page/spitfyah-dragonhead-concept-character-art/ for the win screen picture.