So here is the Rolling Hills Bathymetric PDF, I used for an example.
This is the online program I used to remove the password protection and convert it to a JPG
This is me opening the converted image with Photoshop
Here I've selected the portion of the entire image I want to use, and creating a new image, that I will save as Rolling Hills North
Here I have Google Earth opened up and I'm adding an Image overlay, and selecting the image I saved
Here you select Browse and locate the image.
when you've selected the image it will load, yet likely be way bigger than what you need.
Slide the transparency so you can see both
zoom in on corners once you have it close, and use things like roads to help you. Here you can see the road on both is off by a bit
here its corrected
Things like campgrounds are good to help align. Play with the transparacy slider, quickly going back and forth to see which way the overlay has to move.
Here I've finished manipulating it, and then I'll set the transparency to full overlay (right).
Now we select "add Place-mark"
Here I move the place-mark to the deep oval pool, and name it that. I then highlight the Latitude coordinates and copy them
Next I go to the browser on google, and get me close, or I could just add the coordinates now, but for demonstration I did it this way.