To add custom Journey Builder events or activities to an existing Marketing Cloud app, what must you do?

• A. Create a new distributed package
• B. Register the hosted endpoint in the Marketing Cloud installed package
• C. Create a separate OAuth client for the activity
• D. Publish the app to AppExchange

Answer: (B)

The key idea is how external custom activities connect to Journey Builder. To add a custom activity or event to an existing Marketing Cloud app, you must register the hosted endpoint within the installed package. The installed package is the container that defines and authorizes your integration, and the hosted endpoint is the actual URL that Journey Builder will call when the activity runs. Registering this endpoint tells Marketing Cloud where to reach your service and provides the necessary configuration (like authentication info) so calls from Journey Builder can be handled properly. Without this registration, the custom activity won’t be available or reachable from journeys. The other options aren’t required steps for this purpose: a distributed package isn’t needed to enable the activity in an existing app, and AppExchange publishing isn’t part of configuring Journey Builder integrations.