The program launchers can be found in /usr/share/applications.
Right-click one and select "Open with" and use leafpad. You will see something like:
[Desktop Entry]
Encoding=UTF-8
Name=HV3
GenericName=Web Browser
Comment=HV3 is a lightweight and free multiplatform web browser
Exec=hv3
Icon=/usr/share/icons/browser.png
StartupNotify=true
Terminal=false
Type=Application
Categories=Application;Network;
The above example shows that HV3 is launched using the command "hv3" (find the "Exec=" line). Icon is "/usr/share/icons/browse.png", and it belongs in the "Network" category on the menu.