Instructions
Install the game on your PC and right-click the "Spore" shortcut icon on your desktop. Click "Copy" from the menu that appears. Right-click anywhere on the desktop and select "Paste."
Left-click once on the name of the new shortcut you have created so that it is highlighted in blue. This means it is editable. Type "Flora Editor" and press "Enter."
Right-click on the "Flora Editor" shortcut and select "Properties." Left-click in the input box next to the target so that your cursor is next to the quotation mark after "SporeApp.exe."
Press the "Spacebar" once to make a space after the text already present. Type "-State:floraeditor" (without the quotation marks). For example, if the installer installed your copy of "Spore" in the default location, the text should read "C:\Program Files\Electronic Arts\SPORE\Sporebin\SporeApp.exe" -state:floraeditor" once you are done.
Click "Apply" and then "OK." You will now have a shortcut on your desktop from which to launch the hidden Flora editor. Double-click the shortcut to the start the editor.