Sign in with a google account (make one if you don't have one, or want to have it seperate from your existing google account)
Click the "edit" button thats in the upper right of the box on the left.
Zoom the map into your location.
A little toolbar appears, a hand thing, a pin thing, and a line thing. Click the pin thing.
After you create your placemarker, find it on the list, click it, and edit the info. Don't edit the info in the description box at the top, that isn't for your pin.
After filling the info out for your pin, click Done up near the top of the box, where you first clicked the Edit button.
Also, Eric, someone edited the description box thing. You might want to fix that.