Unfortunately, using custom fonts is not a feature that's currently available in the GoCentral project. I'm sure it's probably on the list of things to do at some point down the road but that's not something you can do on that platform right now.
You may have to consider a platform like WordPress, Drupal, or Joomla (among many others) with greater adaptability.
* Please note that I offer free advice on this forum. I DO NOT PROVIDE ANSWERS VIA PM. If you would like personalized help, you can see my pricing on my services page. Otherwise, please ask your question in the proper forum so the answer can assist EVERYONE in the community and not just you. Thanks! *