NOTE: This if your "Circle" is a saved scene.
Its hard to say what the tree would look like, but you could add a node below the Tilemap
Basiclly heres what the scene tree would look like
----Root Node (Level)
-------Container (Can be a basic node)
In the Container you could add a script where it will spawn/instance that circle as a child of the container node. It is expected that you'll emit a signal to that Container which will Instance you Prefered Scene.