You can easily add custom fonts to the Windows Kiosk app by downloading your font(s), and then copying them into the correct folder. 

With Windows Kiosk closed, browse to: C:\Program Files\Photo Party Upload Windows Kiosk\Fonts, and then paste the font files you want to add (these can be TTF or OTF formats):

Once you reopen Windows Kiosk, the new fonts will be available for Photo Edit options.