How did he do that? I can’t drag a instance collection in a object like him.
He’s using good old fashioned vertex instancing.
Make a collection. Hide the collection. Make a “COLLECTION INSTANCE” from that collection. Put the collection instance as the child of a circle object. Activate vertex instancing.
In my experience if you edit the verts of the circle in any way then the instanced children don’t line up the way you want and there’s nothing you can do about it except make a new circle from scratch. Same with instancing to faces. Geometry nodes gives you full control over how the instanced items are positioned and rotated.