Darkroom Booth uses the fonts you already have on your computer. You can add more fonts by adding those to Windows. Here are some helpful links to find and install fonts.
This is just a few links to font sites. There are many available by searching Google.
The fonts change when I edit a sample template Published
Darkroom Booth screen and print template format embeds fonts into those
files so they can be transferred to other computers. In this way you
can design on one computer while using another for the actual booth. For
copyright reasons we can not install the full font on the PC but can
embed only the letters needed for that template. If you edit the
template and do not have that font on your computer then Darkroom has to
make a font substitution and that is what you are seeing. You may be
able to locate that font online and install it on your computer then
Darkroom would have access to it. Otherwise you can choose another font.