Launch Your Popup in Shopify
1. Log in to your Shopify account. From the Dashboard, select “Online Store” from the left side menu.
2. Select "Themes".
3. Click the "Ellipses button" on the right.
4. From the “Ellipses” drop-down menu, select “Edit HTML/CSS”
5. Click “theme.liquid”.
6. Paste your line of script into your post, anywhere either between <head> and the </head> tags, or between the <body> and </body> tags.
7. Click “Save” to publish your changes.
8. To test your now-live popup, click the “Online Store” button on the left side menu to view your store.
Documentation
9. You're done!