How the Webhooks API Works?



I have my 30-days trial ‘HubSpot’ account.In that I do all the outbound operations.such as if I create any contact in my application it has been created in ‘HubSpot’ also.

Right Now, I have to do Inbound operations.If I create a new contact in ‘Hubspot’ it gets created in my app.
So, I used webhooks API…I have my developer Account on that I created An App and do the webhook subscriptions and submission for crm extensions.

My doubt is,that app has been approved by Hubspot, And I have to integerate that app with my 30-day trial account.then only I do the inbound operations.

Is there any In-built or third-party apps available for these kind of operations.Bro I need clarification on this Bro.kindly help on this.