1.1. Copy the unzipped plugin to "wp-content/plugins/" folder.
1.2. Go to wordpress plugins page "wp-admin/plugins.php" and enable "WooCommerce Raiffeisen payment plugin".
1.3. Go to woocommerce settings payments "wp-admin/admin.php?page=wc-settings&tab=checkout" and set up the plugin. Fill a "Merchant ID" and "Terminal ID".
2.1. Set up callback url like "https://youre_site/wc-api/raiffeisen_callback". You can use API for setting: "https://pay.raif.ru/doc/ecom.html#operation/post-settings-v1-callback"