Oh, if only you could boss fires round like dogs...sadly, 'tis not to be.
It means, "OK, I'm ready for whatever it is you have to say."
Use in Normal SpeechEdit
If someone has something to say but is saying nothing.
"Go on, you look like you're ready to burst. Fire away."
As a request for quetions.
"OK, what d'you want to ask me? Fire away, I'm ready."