The easiest way to send a notification is using a “welcome notification”. Alternatively people can use triggered notifications to send a notification after someone subscribers. If you’d like to go that route, it requires a few extra steps.
Step 1) Add this snippet to site:
//records an event against new subscribers
Step 2) Create a triggered campaign listening for Category: User, Action: Subscribed
Set the delay to as long as you want in seconds, for example: Set the delay to 10800 (that’s 3 hours in seconds)
And that's it! You can now send a notification that is triggered after somebody subscribes. If you have any questions, please reach out to email@example.com