Click on the "Googlemap ME" link at the top of the page
Then you will see this. Slick on "Your entry"
Then this is what you will see. Fill in the necessary info and click on the map approximately where you want the pin located. Then, using the + on the scale at the left you can zoom in until you get in far enough to see the location clearly. You can drag the pin to the exact location. Then click on "insert the information".
This is something similar to what you will see when you have the pin located where you want it. All of this stuff I've put in has been deleted. I just put it in for demonstration purposes.
After you are done this is what you should see.
If this doesn't help out enough I can break it down into smaller segments.