Follow the steps to change/activate WordPress theme from within the database.
1. Log into phpMyAdmin.
2. Click on the wordpress database.
3. Go to the wp_options table.
4. Under the option_name column, locate the template entry.
5. Click Edit next to the template entry.
6. In the option_value column, change the value to the name of the theme.
7. To save, click Go.
8. Click Edit next to the stylesheet entry.
9. In the option_value column, change the value to the name of your theme.
10. To save, click Go.