This is what to do:

1. somewhere in your path create a file named something like
     1600x900.sh
   where 1600x900 = your actual screen resolution
   the config supports 1600x900 and 1680x1050
   It is easy enough to add other resolutions to .fvwm2rc

2. Uncompress fvwm_g3.tar.gz (probably already done)
   You should uncompress under ~/.fvwm
   This will create directory  ~/.fvwm/g3
   with a few files in it

3. maybe review  ~/.fvwm/g3/g3.fvwm2
   and adjust to your needs, this is the
   .fvwm2rc
   see Keyboard section for keys
   2 keys requires wmctrl - http://tripie.sweb.cz/utils/wmctrl/

4. You will probably need to change this file
      ~/.fvwm/g3/modules/FvwmScript-W
   right now it prints a brief weather status
   downloaded from NOAA, you may want something else

5. You may want to Adjust the date format in
      ~/.fvwm/g3/modules/FvwmScript-DTjmc

6. Save your ~/.fvwm/.fvwm2rc
   cp ~/.fvwm/g3/g3.fvwm2 to ~/.fvwm/.fvwm2rc
       *OR*
   link ~/.fvwm/g3/g3.fvwm2 to ~/.fvwm/.fvwm2rc

7. Review ~/.fvwm/g3/Xdefaults and maybe
   merge with your own ~/.Xdefaults (or ~/.Xresources)

8. Ensure all files in  ~/.fvwm/g3/bin
   are executable

9. restart fvwm2

Good Luck