How to Reinstall the Default WordPress Theme

1. Navigate to the WordPress administration area of your website to view the Dashboard. By default, the WordPress administration area is at www.example.com/wp-admin, where 'example.com' is the domain of your website.
2. Open the 'Appearance' menu on the left side of the page, and click 'Themes.'

3. Click the 'Install Themes' tab.
4. Type 'Twenty Ten' in the text field at the top of the page, and then click 'Search.' The Twenty Ten theme should appear first on the list of results.
5. Click the 'Install' link under the Twenty Ten theme.
6. Click the 'Install Now' button. After a moment, the page changes to display the message 'Successfully installed the theme Twenty Ten.'
7. Click 'Activate.'