For Windows systems, place this font in the directory \Windows\Fonts. For Linux, place it in /usr/share/fonts (there may be some distribution-dependent variations in this location). Next, for all platforms, run wxMaxima and go to the menu item "Edit ... Configure ... Style tab", select "Use Greek Font", then click the "Greek" button, navigate to and select the font you have just installed.
The change should take effect immediately. To test the ability of wxMaxima to render correctly, type examples of Greek characters in wxMaxima using this notation:
%Omega;The results shown above indicate success. If your typed strings reappear in the output unchanged, something went wrong — go over the instructions above and repeat any steps you missed.
Thereafter activate this font in wxMaxima, from Edit>Configure>Style>Use greek font