Adding custom CSS to your theme

CSS (Cascading Style Sheets) is coded file that selects elements of your page and controls their presentation. Think of your custom template's HTML as the bones of your website and the CSS as the skin of your site.

Please refer this article from Shopify for Adding custom CSS to your theme: https://help.shopify.com/en/manual/online-store/themes/theme-structure/extend/add-css

Add Custom Css in Theme Settings

Custom CSS can be added to your entire theme that affects all pages in your online store except the Checkout page. For example, you can change the way that buttons are displayed across your entire store.

Steps:

1. In your Shopify admin, go to Online Store > Themes.

2. Find the theme that you want to edit, and then click Customize.

3. Click Theme settings -> CUSTOM CSS.

4. Add your code and click Save.

Your css will be saved in settings_data.json file

Add Custom Css in Section

Custom CSS can also be added to a specific section of your theme. For example, you can apply a custom font size or a background color to a single section.

Steps:

1. In your Shopify admin, go to Online Store > Themes.

2. Find the theme that you want to edit, and then click Customize.

3. Click the section that you want to add CSS to.

4. At the bottom of the section properties panel, click Custom CSS.

5. Add your code and click Save.

Your css will be saved in index.json file