There's a property in the Tilemap called "PositionToTile". Check out the Tilemap entry in the manual, there's all kinds of important techniques you can use to go back and forth between Layout and Tilemap coordinates.
In your screenshot, if you use:
Tilemap.PositionToTileX(Player.X)
Tilemap.PositionToTileY(Player.Y)
That will use the Tilemap tile XY instead of the Player's layout XY.