When you find the center for your circle using Google Earth (just open it and put your cursor where you want the center to be), Google Earth will give you the Lat/Lon in the degrees-minutes(')-seconds(“) format. Circle Generator 2 uses decimal format when inputting Lat/Lon, so you will have to convert.
The radius field is pretty straight forward: its the radius of your circle in meters. Make sure you convert any other value(km, miles, etc.) to meters.
This value is inconsequential, as Google Earth will automatically re-size the window to fit your circle.
This is the name you'd like to give this file. Its a good idea to put in some info about how large the circle is or where its located. Make sure its extension is .kml before you hit the “Create File” button.
Once all of your fields are correct, click the “Create File” button. This will create a kml file and save it to your Desktop. Once it appears, double-click the icon to open your circle in Google Earth.
When you open your kml file, your circle appears in Google Earth. It's usually a good idea to double-check the radius length using the Ruler button at the top of the screen in the toolbar. Set one end to the exact center of your circle (zoom in if you have to) and then place the other end on the circle. The ruler window lets you view the distance in a variety of units.
You can edit the color and line thickness of your circle by finding your file in the list of places on the left and right-clicking on it. Click on “Properties”, and in that window click on the “Style, Color” tab. Click on the color box to bring up a color select window. You can choose a basic color, or find your own. Once you find the perfect color, you can add it to your custom colors for future use (i.e. you're making more than one circle of that color). You can also adjust the width and opacity here.