you need to create a http-endpoint in your mule flow, and specify to which URL it should listen to. example of such endpoint declaration is:
<http:endpoint name="myEndpoint" address="http://myExample.info/exampleAddress" exchange-pattern="request-response"/>
update
set the address for endpoint to the available port, so if 80 is not occupied - it's ok to have it for example address="http://localhost:80/exampleAddress/"