Source : http://dev.wechat.com/wechatapi/installguide
Build your First Application with WeChat SDK!
Note: This document describes how to develop an app using WeChat SDK. You should already be familiar with the XCode environment.
1. Register App ID
Fill in the required details on the App Registration page to obtain an AppID. Submit the registered app for approval. Approved apps will be released.
2. Download the SDK package
The package comprises three files: libWeChatSDK.a, WXApi.h, WXApiObject.h
Download: iOS SDK package
3. Build your development environment
 Create your project in XCode.
 Add the following three files to your project: libWeChatSDK.a, WXApi.h, WXApiObject.h; for example, you can create a project called Test, and add these files to the project’s directory.
Note: For XCode 4.3 and earlier versions, please use libWeChatSDK.a. For XCode 4.5 and later versions, use libWeChatSDK_armv7_v7s.a
 Choose the “Build Setting”. Then add the paths of the following files to “Search Paths”, as shown below: libWeChatSDK.a, WXApi.h, WXApiObject.h.
Note: For XCode 4.3 and earlier versions, use libWeChatSDK.a. for XCode 4.5 and later versions, please use libWeChatSDK_armv7_v7s.a
 In Xcode4, select “TARGETS”>”Info”>”URL type”>”URL scheme”. Add the ID for your registered app. For Xcode3 and earlier versions, please add the ID to your plist file, as shown below.
URL scheme settings in Xcode4
 For files on which you want to use the WeChat API, import WXApi.h and add the WXApiDelegate protocol.
#import <UIKit/UIKit.h> #import "WXApi.h" @interface AppDelegate : UIResponder <UIApplicationDelegate, WXApiDelegate> @property (strong, nonatomic) UIWindow *window; @end
4. Start Coding
Now go ahead and start coding!