curl -u admin:admin -X POST http://localhost:9000/api/campaigns -H 'Content-Type: application/json' -d '{"name":"June Newsletter","subject":"Hello, world","lists":[1],"content_type":"richtext","type":"regular"}'

Creates a campaign in draft status; name, subject, lists, content_type, and type are required. A campaign is one newsletter send to the target lists. Add body with template markup and template_id to use a custom template, then test and schedule it before it goes out.