If for some reason you can’t perform automatic updates through your WP Admin panel then you can manually update the plugin to the latest stable version by taking the following steps.
Using WP Admin & a plugin
2. Install the Easy Theme and Plugin Upgrades plugin (free).
3. Navigate to WP Admin > Plugins > Add New > Upload.
4. Select “Yes” for the “Upgrade existing plugin?” option.
5. Browse to the location of the plugin ZIP file on your computer and press “Upload”
2. Unzip the downloaded ZIP file somewhere on your computer
3. Connect to your webserver over FTP and navigate to `/wp-content/plugins/`
4. Locate the plugin directory: `mailchimp-for-wp-pro` or `mc4wp-premium`.
5. Replace the entire directory with the files from the downloaded .zip file.
By following any of these two methods to update the plugin you will never lose any of your configuration settings.