This tutorial will show you how to delete installed theme in WordPress
Remove theme from admin panel
1. Open WordPress admin panel
2. Go to Appearance>Themes
3. Activate the default WordPress theme (Twenty Ten). You can’t delete the active theme. Do not delete the default WordPress theme.
4. Now you can delete any other theme. Use the Delete link under the theme thumbnail
Removing theme through FTP
1. Using FTP manager login to your server and open the WordPress installation folder
2. Go to wp-content/themes and delete the required folder.
Feel free to check the detailed video tutorial below:
How to delete WordPress theme