Hi Gmach, I've tried looking elsewhere, but the best way it seems, without using a 3rd party software, is taken from the User guide that I guess you already have and is the method Freddie suggests.
http://garmin.com.ua/manuals/air/GPS...ilotsGuide.pdf Page 58
You simply have to create a waypoint and then change the information before it is saved. As long as you have 2/3D coverage, you can do this either 'at home' or in the air.
Then it's a matter of - 'Goto' - 'New waypoint name'.
Hope it helps