The Guide shows you Howto Make/Create/Add a New Application Launcher Item into the Main Menu on Linux Peppermint 3 Lxde Desktop.
And this Visual Guide includes the Basic Screenshots of All GUI Steps involved.
The Practical Example Shown Up here is About Making a Firefox Nightly Launcher, on the Bottom you Find Link to Setup Firefox Nightly for Lubuntu.
The Content give Focus Only to the Essentials Instructions and Commands to make it Easier to Follow.

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Open Terminal Window
(Press “Enter” to Execute Commands)In case first see: Terminal QuickStart Guide.
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Start the Lxde GUI Creator
lxshortcut -o /usr/share/applications/nighlty.desktop
Alternatively you can Create the Launcher also Into: /var/lib/menu-xdg/applications/menu-xdg.
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Insert Name and Command
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Set the Launcher Icon
Click on “Change Icon”.
Try to Search the Icon between the Defaults One.
Now if you Do Not Find it Look:
How to Locate Icons/Images