Having to do some digging in my old theme code but if I remember correct, you can include fonts in a css block ([[code type="css"]] to [[/code]]) with the command @import.
This would look like @import url('https://fonts.googleapis.com/css2?family=Charm:wght@700&display=swap'); as this uses the google fonts link for Charm. Replace the url with the google fonts link for your desired fonts. As well, the command "—title-font: 'Charm', cursive;" can be used to inject the font to replace either the header, body, title, or mono fonts with a font of your choice. You'll have to specify the font name and subtype in the command, as well as the specific section you're trying to replace (header, body, title, or mono).
To replace the title font with Charm, here's the code you'd use:
"[[code type="css"]]"
"@import url('https://fonts.googleapis.com/css2?family=Charm:wght@700&display=swap');"
"—title-font: 'Charm', cursive;"
"[[/code]]"
Since this is a CSS code block, when you remove the quotation marks it'll disappear and run the code. You should stick this at the very front of your story to have it work right.
If you have any more questions, let me know!
