Shane - man this song has taken some tracking down. I first found it was on 1983 Life, a live album, but not on a studio album.
According to below (which I got from YouTube) it came out in 1981 on a Live EP. (Putting all this here in case it goes into a Top100, and so I know where to look on GooglePlay to listen to it ;)).
Not to be confused with the earlier track of the same name by Pacific Gas & Electric, "Are You Ready" was co-written by drummer Brian Downey, lead guitarists Scott Gorham and Brian Robertson, and Phil Lynott. Bass player and group leader Lynott wrote most of the band's material, and the lyrics were probably written by him alone. "Are You Ready" is an uptempo number that was often used as a show opener, a prelude of a night's heavy rocking.
The song title has no questionmark, possibly because the question is rhetorical. In April 1981, it was released on a live EP called Live Killers along with "Dear Miss Lonely Hearts" and the B Side, "Bad Reputation".