Using webhook to push notifications iOS

I am using an API which doesn't support direct iOS notifications instead they use webhook. When I contacted them about how to use it I got back the response

We DO NOT support iOS push notification directly to your client apps. You can make use the webhook notification to receive the update, then your script can relay or send out the notification to your clients app directly.

I am given a place to enter a URL for the webhook.

What do I need to do to setup notifications for iOS using what I have been given?