1. Navigate to a page or template where you would like to add the code. 
  2. Select Edit this page.
  3. Click in a content pane where you would like the code added. > Select New part.
  4. For part type, select Unformatted text and click Next.
  5. Paste the code in the part editor.
  6. Mark the checkbox to Show Advanced Options.
  7. From the placement in HTML drop down, select At the end of the <body> tag.
  8. Save.

For more information on Adwords and Remarketing code from Google, please refer to Google's user guide.