How to track new user post Instagram API

I'm looking at Instagram's subscription API and I would like to track new posts made by a user.

I have the callbacks set up correctly that when I send a curl request

 curl -F 'client_id=clientId' \
 -F 'client_secret=clientSecret' \
 -F 'object=user' \
 -F 'aspect=media' \
 -F 'verify_token=myVerifyToken' \
 -F 'callback_url=callback' \
 https://api.instagram.com/v1/subscriptions/

I get a 200 response.

{"data": 
   {"id": 0, 
    "type": "subscription",
    "object": "user", 
    "object_id": null,
    "aspect": "media", 
    "subscription_id": 0, 
    "callback_url": "callback"}, 
    "meta": {"code": 200}
 }

But I don't see how the curl above would subscribe me to a user. I saw this post Instagram API - How to Subscribe to a specific User

Apparently you pass in the access token and user id like this

 curl -F 'client_id= ci' 
      -F 'client_secret= cs'  
      -F 'object=user' 
      -F 'id=user_id' 
      -F 'aspect=media' 
      -F 'verify_token=authenticaiton_token' 
      -F 'callback_url=callback' 
       https://api.instagram.com/v1/subscriptions

But this returns the same response. I don't see any more detail on the documentation on how to format the POST request to track new user posts

via testinggnitset ser