Find a site that distributes them, select the font, pay the fee if it's a
commercial site, click the download button (or whatever the site uses as
such) ...
When you've found a site that supplies the font you want, download it and
unzip it if necessary. You then need to go to Windows Control Panel and
double click on the Fonts folder. Click on File -> Install New Font and
navigate your way to the font you downloaded, it should then be installed for
you.