Surprisingly it is not straightforward to draw a circle in Google Earth. Googling led me to this KML Circle Generator web form which is currently not working. Submitting the form leads to “Go back and make sure you have entered the values we need”. So I found this alternative which does the trick.
Browse to Google Maps and paste the following URL into the “Google” search field:
Modify the URL with your own lat, lon, radius, units*, and geometry colour and press Enter. Google Maps displays your location as the center of a point radius.
* Supported units are kilometers, miles, meters, feet and km.
To view the circle in Google Earth paste the same URL into the URL address field of your browser and press enter. The file “circle.kml” is generated and downloaded by the browser. Browse to your download folder and open the KML file in Google Earth and wholah.