There is a specific example in the readme about circles...
[{"id":"c0e71a8c.e22e48","type":"inject","z":"dfe4ec36.0a5a5","name":"","topic":"","payload":"{ \"lat\":51.05, \"lon\":-1.35, \"name\":\"A3090\", \"radius\":3000 }","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":170,"y":1180,"wires":[["f22e5b4f.f7bf28"]]},{"id":"f22e5b4f.f7bf28","type":"worldmap","z":"dfe4ec36.0a5a5","name":"","lat":"","lon":"","zoom":"","layer":"","cluster":"","maxage":"","usermenu":"show","layers":"show","panit":"false","x":370,"y":1180,"wires":[]}]
