To use a webhook, add it to a smart campaign as a flow action.

Not all customers have purchased this functionality. Contact your sales rep for details.

Create a smart campaign.

Webhooks can only be used in trigger campaigns.

Go to the Flow tab and drag in the Call Webhook flow action.
Select the Webhook.
You can also use Webhooks in a smart list.
Finally, you can use Webhooks in Add Choice in a flow step.

Learn more in the Webhooks deep dive!