I would not recommend that link to the Ubuntu community. It suggests things that require additional programs for what is a very simple task that needs no additional programs.
I'm not sure what 666lawyer wants to do. Have Firefox start automatically when IceWM starts? Or have Firefox in the menus? (Firefox is included in VL6 Light and should already be in the menu.)
To start Firefox when IceWM loads, edit the ~/.icewm/startup file with a line like this:
# start Firefox
Save, log out, and restart IceWM. Let us know if this works or not.