Allows you to select the font, size, line height, and QuickView font settings.
To choose your font you must go to https://fonts.google.com and paste the exact name in the space provided.
10 STEPS
1 The first step is to open the Theme settings of your Shopify theme config and go into the Typography settings.

2 To choose your font go to https://fonts.google.com and locate a font you would like to use, paste the font name in the input box.

3 Select any font family

4 Copy this Font Name.

5 Paste here the Font Name, which you want to use for the store. Here in our case have replaced the 'Oxygen' font with 'Roboto'.

6 Now Select Default Font Size and Default Line Height.
Default Font Size => This will be default Font size for your Store.
Default Line Height => This will maintain space between two Lines.

7 Quickview => When you hover the product Quickview button appears. You can change the Font size and style.
Quickview Font Size => Select the font size.
QuickView Font Style => Select the font style, here we have selected Bold.

8 Now Click Save

9 Here you can see the Quick Buy button in action.

10 That's it. You're done.

Here's an interactive tutorial for the visual learners
https://www.iorad.com/player/1583552/DemoStore----Typography
Default Font: The default font that will display site wide.
Default Font Size: Choose the best font size for readability and branding.
Default Line Height: Determines the amount of line spacing.
Quick View Font Size: Choose the best size for readability and branding.
Quick View Font Style: Make your font light, normal, bold, and bolder
Click “Save” and continue with setup.