You can set a var as your location like
onready var Sprite_position = Vector2()
set your sprite for an instance like
Sprite_inst = preload("res://Sprite.tscn")
and then you can use the randrange to set its positions for example
Sprite_position.x = rand_range(1, 100)
Sprite_position.y = rand_range(1, 100)
create an instance of your sprite like this
Var New_sprite = Sprite_inst.instance()
and then put it in the random position you created with
New_sprite.position = Sprite_position
finally add it to the scene
add_child(New_sprite)
Hope this helps.