Update README.md

Author: wangjiejacques

README.md

@@ -1,6 +1,12 @@
 # Installation
-`git clone https://github.com/WANGjieJacques/CodeGenerator.git`
-The app is in app/CodeGenerator.app.
+1. Clone or download the repo
+2. Open ``CodeGenerator.xcodeproj``
+3. Enable target signing for both the Application and the Source Code Extension using your own developer ID
+4. Select the application target and then Product > Archive
+5. Export the archive as a macOS App
+6. Run the app, then quit (Don't delete the app, put it in a convenient folder)
+7. Go to System Preferences -> Extensions -> Xcode Source Editor and enable the CodeGenerator extension
+8. The menu-item should now be available from Xcode's Editor menu
 
 # CodeGenerator
 CodeGenerator is a Xcode extension for swift code generation.