While you cannot use your own font on Logojoy.com, you are free to use it in your logo after you purchase the Premium or Enterprise package.
You can open the vector files found in our Premium package and in our add-ons, in a graphics editor and use your own font. With the Enterprise package our graphic designer can customize your logo for you with your font if you provide the .TTF or .OTF font files for them.
Take a look at this article to learn more about editing and using your vector files.
For additional information on using our logo editor's fonts, review this article on changing your font.