Find the VRCFury prefab for the sprinkler(s) in the ‘RuneFox/Sprinklers/_Prefabs’ folder and drag it into the scene and then onto your avatar’s hierarchy so that it becomes a child object of your avatar.
If you want to change the location in front of your avatar that the sprinkler is placed at then simply move either the prefab’s root object or the RootTarget gameobject within the prefab itself.
You should be good to upload the avatar.