How to change the fonts?

1. Upload Font

This feature will allow you to upload the custom fonts to the app and apply them to your site. Please follow the below steps:
Step 1: Prepare your custom font file with the format are ttf / woff / otf. You can find it at https://www.fonts.com/, https://webfonts.ffonts.net/, https://www.dafont.com/...
Step 2: From the App dashboard, click Upload Font
Or you can go to Fonts -> Create new button to upload your fonts.
Step 3: Click on Add file to select your font file and fill in the Font name option.
Step 4: Tick the options that you want to assign the font to.
For example: I want to change the font for the headlines, so I can tick the Headline 1 to Headline 6 options.

Note: You can tick “All” if you want to make changes to all elements of your store.

Note: You can use Element Picker if you want to make changes to specific parts of your store. Simply click on the Polaris icon to select the elements that you want.

You will see your store preview. Hover over the text element and click on the select text to select whatever elements you want to apply to the new font. After done for the selection, you can see the class name of the elements that you select in the Custom Elements box.

Step 5: Tick Overwrite other fonts option to overwrite the new font to the font in the Shopify theme. 
Step 6: You can choose a language or a specific page where this font will be applied.
Step 7: Set Font visibility is Active and click Save
All done, please wait about 1-2 mins and then reload your site to see the result.

2. Google Font

Step 1: From the App dashboard, click Add new font button.
Step 2: Open the Google fonts tab and click on Choose font to select a font.
Then find the font that you like and select it.
Step 3: Please do similar steps with Upload font
Step 4: Unlike uploaded fonts, Google Fonts can be optimized.

Font Optimization helps improve your store’s performance by giving you full control over how Google Fonts are loaded.

By limiting unused font weights, styles (normal/italic), and language subsets, your store can reduce font file size, improve loading speed, and enhance overall performance—especially on first page load.

After all done, click Save and wait about 1-2 mins and then reload your site to see the result.