How to install these icons on the desktop？
By default NomadBSD uses Openbox which hasn’t a desktop (just a root window) on which you could place icons without further software. If you want a desktop with icons, you can start
pcmanfm --desktop. You can enable the trash icon in its settings. For the home-icon copy ~/.local/share/applications/home.desktop to ~/Desktop (the name depends on your language.
xdg-user-dir DESKTOP will tell you).