Get The Picture Meaning

(idiomatic) To understand or comprehend; to interpret correctly.

Example:   I hung a "no solicitors" sign by my door. One of these days, I hope they'll get the picture and quit ringing the bell.
1910 Dec 1, “Round About Chicago”, Chicago Tribune:
  Get the picture? In one corner Charles Edward Russell, champion muckrake pugilist of the world. .. "In the opposite corner wel have Scribbling Bill Dare