added documentation

DOCUMENTATION/content/documentation/index.md

@@ -1490,6 +1490,23 @@ docker-compose exec tarantool console
 7 - There you can operate with tarantool database ([official documentation](https://www.tarantool.io/en/doc/latest/) can be helpful).
 
 
+<br>
+<a name="use Keycloak"></a>
+## Use Keycloak
+
+1. Run the Keycloak Container (`keycloak`) with the `docker-compose up` command. Example:
+
+```bash
+docker-compose up -d keycloak
+```
+
+2. Open your browser and visit the localhost on port 8081:  `http://localhost:8081`
+
+3. Login with the following credentials:
+
+    - Username: `admin`
+    - Password: `secret`
+
 <br>
 <a name="CodeIgniter"></a>