Image Sizes Available
- Sidebar Featured Square 75×75
- Featured Rectangle 325X480
- Featured Rectangle Big 380×560
You can download the plugin on wordpress.org/plugins/regenerate-thumbnails or simply search for Regenerate Thumbnails on Plugins → Add new in your WordPress backend to install the plugin.
After you have installed and activated the plugin, you can regenerate your thumbnails on Tools → Regen. Thumbnails.