update readme

README.md

 ![logo](/arts/fluwx_logo.png)
 
-# fluwx
+适用于Flutter的微信SDK，方便快捷。
 
-A new Flutter plugin for Wechat SDK.
 
-## Getting Started
+## 写在前面
 
-For help getting started with Flutter, view our online
-[documentation](https://flutter.io/).
+ 使用Fluwx之前，强烈建议先阅读[微信SDK官方文档](https://open.weixin.qq.com/cgi-bin/showdocument?action=dir_list&t=resource/res_list&verify=1)，
+ 这有助于你使用Fluwx。Fluwx的api字段名称基本和官方的字段名称是一致的。
+## 引入
+## 初始化
+ ```dart
+    Fluwx.registerApp("yourAppId");
+ ```
+或者
+ ```dart
+ Fluwx.registerApp();
+ ```
 
 For help on editing plugin code, view the [documentation](https://flutter.io/platform-plugins/#edit-code).
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