Start by ensuring that you have the RB2B script ready. You can find it in the Script section of the dashboard. Copy the entire code snippet to your clipboard, preparing it for embedding into your Shopify site.

Log in to your Shopify admin dashboard and navigate to the Online Store section, then click on Themes to view your current theme selection.

Locate the theme you wish to modify and click on the … button to access the actions menu. From this menu, select Edit code to enter the theme's code editor.

Within the code editor, you'll see a section titled Templates. Here, click on any of the .liquid files you've recently worked on or intend to modify.

Add your RB2B tracking script, as provided in the dashboard, just above your </head> tag and click Save to publish your changes.

To ensure your changes have resolved any issues without introducing new ones, you can preview your store. Click on Preview store to see the effects of rolling back to an older version of the .liquid file.

By following these steps, you can confidently edit or revert changes within your Shopify theme's code. If you encounter any difficulties or have further questions, don't hesitate to reach out for additional support.