Hi Candan,
Thanks for pointing this out. This part of the User Manual is quite old.
Once you install Collect Earth in your computer it should be accessible through a Collect Earth shortcut on your desktop or the Windows start menu.
If you don't find it there you should be able to find it in *C:\OpenForis\CollectEarth\CollectEarth-launcher.exe *_C:\OpenForis\CollectEarth\CollectEarth-launcher.exe_