How to add custom CSS code
To make basic theme customisations we sometimes provide CSS code that you can apply to your theme. Here are the steps on how to do it:
1. Head to the themes area of your Shopify admin https://shopify.com/admin/themes
2. First thing you should do is duplicate your theme for safety backup if anything goes wrong. To do this look for the 'Actions' dropdown button next to the 'Customize' button and select 'Duplicate'.
3. Now you need to edit your code - again look for the 'Actions' dropdown button next to the 'Customize' button and click 'Edit code'.
4. When the code view appears scroll down and find the 'Assets' folder on the left of the window. Inside that is the 'theme.scss.liquid' file (for the themes older than version 4, the file is named 'main.scss.liquid').
5. Scroll right to the bottom of this file and once you can go no further paste in the CSS custom code.
6. Lastly save your work and then check that all is working as expected.