One way is by digitizing by hand. Import and plot the graphic, right-click and choose "Get Coordinates." You now have a cursor that you can move around in the graphic. Each left click will draw a marker. When you have the markers you want, ctrl-c (Windows) will copy the list of coordinates. Ctrl-v will paste them. You can paste them in a next cell and assign them as a list of coordinates to a variable. It's up to you then to scale them as needed. If the graphic has a real-world scale, they will be immediately usable. At times, I have digitized several known features in a graphic and used the relationship between graphic coordinates and real-world values to define a transform for scaling.

Best regards, David