Log in to your WordPress admin panel and go to: Plugin > Add New and click on Upload Plugin.
Select the zip file and click onĀ Install Now. After clicking that link, you will be asked if you are sure you want to install the plugin. Click yes and WordPress will automatically complete the installation process.
No configuration needed.
Once installed, Smush will automatically compress new images. If you would like to compress current images. Go to the Smush plugin and click Bulk Smush.
*Note: It will only allow 50 images at a time.
For more information about Smush, you can visit https://wordpress.org/plugins/wp-smushit