Start off by finding the place it is that you are looking for on google earth. Once you have found the exact place you looking for go select this tool from the options bar on google earth:
Once you have selected the 'ADD PLACEMENT' a yellow drawing pin will come onto your screen. Using your mouse and the left mouse botton, click on it and drag it to your desired destination. Your screen should now look like this:
Now go into the dialog screen and add in all the details you want this placemark to have. As such:
Dont worry about Style, View and Altitude. Once you are happy with the name of the place simply click "OK"
On the left hand side of the screen your Placement will be put into the toolbar.:
Now left click once on that placemark you have just created and it should highlight it for you. Then RIGHT CLICK and select "SAVE PLACE AS".
Select the folder in which you would like to save the file. The name will automatically become the name of your placemark. You are more than happy to change it if you want. The "SAVE TYPE AS" will also automatically come up as a '.kmz'
Now simply left click on the save button and thats your .kmz file saved.
Enjoy