Customize
Open the theme editor
Jump straight from the app into Shopify's theme editor.
From My Sections
Go to My Sections.
Find the Theme Editor card at the top of the page.
Click the Customize in dropdown.
Choose the theme you want to edit.
The Shopify theme editor opens in a new tab.
From the Home page
Open the app Home page.
In the setup guide, click Open Theme Editor.
From Shopify admin
Go to Shopify admin → Online Store → Themes.
Click Customize on the theme you want.