Unfortunatley the short answer is you can’t @LWDJR. There may be workarounds depending on what you are trying to do so if you are in a position to share more around your use case please do. The Webhooks API only supports Contacts, Companies and Deals. If you are triggering webhooks from workflows you are limited to Contacts, Companies, Deals, Tickets, Conversations, Feedback and Custom Objects.
Ok, well then I guess your next best bet is to reach out to HubSpot (I’ll be doing the same), I’ve also checked my app and I can’t see options to subscribe to changes happening for any of those objects listed:
Not sure if you’ve done so already but in case you haven’t… I reached out to HubSpot Support and it turns out that the items included in that update where a typo and are actually in private beta, see below from my interaction.
This feature is in private beta status currently however it appears the update referenced here was a mistake and the plan is for this feature to be rolled out in December of this year. So as of now the ability to create webhook subscriptions for these object types is not live and we unfortunately cannot grant access.
So until December of this year it looks like this isn’t supported using the Webhooks API. Also, that rollouts doc has been updated since I’ve reached out.