Create a new application.
In order to get rid of a warning that your users will see before installing Hubspot module, you have to verify your identity as an app provider.
You can manage the Contact & Support settings.
Or skip for now.
Set the application name, logo, and description.
Go back to Hubspot and set the redirect URL, replace acme.com with your domain and keep the suffix /auth/hubspot/callback
One more thing that you will need is the Hubspot, go back to the Apps page and hit the Get HubSpot API key button.