To install Unless into Shopify, follow these steps.

1. Start by logging into your Shopify account and navigating to your dashboard.
2. Click "Online Store". 

3. Select "Theme" from the menu bar, then click on the dotted dropdown menu in the right upper corner and then click "Edit HTML/CSS".

4. Select "theme.liquid" under "Layout".
5. Scroll down to the bottom of the theme.liquid file and insert the Unless script above the closing HEAD tag (</head>).  
6. Then, scroll back to the top and click Save.

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