- Go to your store's admin area.
- Click "Storefront" > "Theme" in the dashboard navigation.
- If the "HTML / CSS" button is disabled, first click the "Duplicate" button. This will make a copy of your Theme so that you can safely make changes, knowing you'll be able to go back to a stock Theme.
- If you duplicated your current Theme, click the "Use This Theme" button on the duplicate Theme.
- Click the "HTML / CSS" button.