doc: add usage of dashbaord

Author: gxthrj

README-dashboard.md

@@ -60,6 +60,22 @@ yarn lint:fix
 yarn test
 ```
 
+## Usage
+
+### 1. start manager-api
+
+
+[Configure and Installation manager-api](api/run/build.md)
+
+
+### 2. login dashboard
+
+Visit `http://127.0.0.1/dashboard/` in the browser, Enter `http://127.0.0.1:8080/apisix/admin` into the first input box, this is the backend management service address
+
+![login](compose/pics/login.png)
+
+now, click `save`.
+
 ## More
 
 You can view full document on our [official website](https://pro.ant.design). And welcome any feedback in our [github](https://github.com/ant-design/ant-design-pro).