You can change the fonts for different elements on your website at a site-wide and stack-specific level. Please see below how you can do this:
To change fonts at a site-wide level, click on Change Design in the top left-hand corner of your site.
Depending on what you want to change the fonts for, click on the relevant panel and select the font you want:
You can now choose what font you like to use from the dropdown.
If you cannot find the font you are after please head to 'Add Font' and follow this guide here: How to add/remove custom font to your Rocketspark website?
Changing fonts on a stack-specific level is the same, except you, will need to do it from the Stack-specific design panel. Hover over the stack you want to edit and click the Edit Design colour wheel:
And then select which section of the Stack-specific design you would like to change the font for.