To add an item to a menu for all users, perform the following steps:
Create a desktop entry file for the item that you want to add. For more information on desktop entry files, see Desktop Entry Files.
Open a file manager window. Choose File -> New Window to open a second file manager window.
In one window, access the location where you want to add the menu item. For example, to add a menu item to the Preferences menu, type preferences-all-users:/// in the Location field, then press Return.
In the other window, select the desktop entry file that you created for the menu item. Drag the desktop entry file to the location where you want to add the menu item.
Alternatively, you can copy the desktop entry file, then paste the file into the location where you want to add the menu item.
The next time users log in, the menu item is in the assigned location.