fix wrong url

Signed-off-by: Xiang Dai <764524258@qq.com>

README.md

@@ -192,6 +192,11 @@ datasources:
     basicAuthPassword: test_password
 ```
 
+Make sure to adjust the url and authentication to your needs, the url should be:
+- `http://localhost:3100` when run Loki locally
+- `http://loki:3100` when run Loki with docker or docker-compose
+basicAuthUser and basicAuthPassword should same as your Grafana setting.
+
 ## Further Reading
 
 - The original [design doc](https://docs.google.com/document/d/11tjK_lvp1-SVsFZjgOTr1vV3-q6vBAsZYIQ5ZeYBkyM/view) for Loki is a good source for discussion of the motivation and design decisions.