If you want to change all the fonts of your presentation, you can do so in the master slides. But as SlidesCarnival presentations were originally created in Google Slides, changing the fonts in the Master slides might not work. To solve this issue:
1. Click the Replace drop-down arrow, located on the Home tab, in the Editing group, and choose Replace Fonts.
2. Under Replace, choose the font you want to replace, and under With select the new font that you’ll use. Once you’re done, click Replace to apply the changes.
3. The new font will be applied to your presentation.