Arrive, become available for use or begin to produce, as in Has the new fall line come in yet? or The latest reports are coming in now, or This well has just begun to come in. [Late 1800s]
Also, come in on. Join an enterprise, as in Do you want to come in on our venture? [Mid-1800s]
Be one of those who finish a contest or race, as in My horse came in last. [Late 1800s]
Perform or function, as in This mixer comes in very handy, or Where does my department come in? [Late 1800s] Also see come in handy.
Enter into an account, issue, or list, as in Where does this question come in? or Please explain where in this long process I come in. This usage dates from Shakespeare's time and appears in The Tempest (2:1): "Widow? A pox on that! How came that widow in?" Also see subsequent entries beginning with come in; come into; this is where I came in.