To add a new tab with the own manageable content to the product details page:

  1. In the administration panel, go to Design > Product Tabs.
  2. Click the + button to add a tab. In the opened window:

    1. Enter the tab name (e.g. New tab).
    2. Select whether you want to show the tab as a popup window using the Show this tab in a popup window checkbox.
    3. Click the Select Block button and choose the HTML Block in the appeared window in the Create New Block tab. In the appeared window: 
      1. Enter the tab name (e.g. Specifications).
      2. Specify block content in the Content field on the Content tab.
      3. Click the Create button.