Answer
If the x-coordinate is positive, then move that many units to the right from the origin. If the x-coordinate is negative, then move that many units to the left from the origin.
If the y-coordinate is positive, then move that many units above the origin. If the y-coordinate is negative, then move that many units below the origin. The y-coordinate is acted upon after the x-coordinate. (You move horizontally before you move vertically.)
If either the x-coordinate or the y-coordinate are zero, then you don't move horizontally or vertically, respectively.
Work Step by Step
As an example, let's plot the point (4,1). Since the x-coordinate is positive 4, we move four units to the right of the origin (0,0). Since the y-coordinate is positive 1, we move up one unit from the point (4,0).