This is a tool that allows you to take a picture that has an obvious origin and scale to it (say a map) and quickly scale the picture to the correct boundaries. First:
Insert the picture
Then click on the tool
Click where you'd like the origin to be
Click on the bottom left corner of the picture
Click on the upper right corner of the picture
Click on the beginning of a measuring scale
Click on the ending of a measuring scale
Type in the size of the measured length
This produces an Xmin, Xmax, Ymin, and Ymax values for the new picture.
Then click on your picture and set the position of the corners to be those values.
