PlayOneShotAttached is a function of the RuntimeManager, you can call it like this:
FMODUnity.RuntimeManager.PlayOneShotAttached(dartGunShoot, location);
The event will get added to a list and update with the gameObjects transform, you can use PlayOneShot() to fire an event that doesn’t update position.
Alternatively can use the StudioSystem to create and play an event and attach it to a gameObject so that you can still use the event reference.
FMODUnity.RuntimeManager.AttachInstanceToGameObject(instance, transform, rigidbody);