1. On the top menu, click Admin.
2. In the left sidebar, click Marketo Custom Activities.
3. At the top of the page, click New Custom Activity.
4. In the New Custom Activity window, enter the display name.
5. Review or edit the API Name, then enter a description.
6. Click Next.
7. Enter the Filter and Trigger labels for the custom activity.
8. Click Next.
9. On the top menu, click Fields.
10. Enter a name for the primary field that summarizes the custom activity.
11. Click Save.