you can also do it manually if you want, without using GE Plus (if you are so inclined). Here's an example of the code:
Easy enough, once you understand what's going on. You can get your coordinates from your other placemarks.
<name>Name of placemark</name>
<Icon></Icon> <!-- this is to have no icon appear in My Places; you can have an icon if you want, though -->
<width>2</width> <!-- width is between 1 and 4; I think that default is 1 -->