For such questions it is convenient to choose the "base" to be a segment that is aligned with one of the coordinate axes. Here, the horizontal segments will serve. Their length is the difference between the x-coordinates of the end points, -2 -(-6) = 4, for example.
The height is measured perpendicular to the base, so will be the difference between the y-coordinates of the horizontal segments: 2 -(-4) = 6.
