First, to use Blogger Classic Template, you have to convert your template to classic template. To convert or revert blogger themes to Blogger Classic style:

  1. After Login, you can choose ‘Layout‘ on blog that you want to modify or edit.
  2. On Template tab, choose ‘Edit HTML‘.
  3. Scroll down, below ‘Edit Template’ form, you will find ‘Revert to Classic Template‘ links. Choose that link to convert, follow the step.

THEN, to change with the new template:

  1. Copy all code from new template file that you’ve download.
  2. Paste it to the form ‘Edit HTML’.
  3. Click ‘Save Template Changes’.
  4. Open you blog, if there’s no changes, click F5 or Ctrl+F5 to refresh your browser.

Have fun with new template ;)