When opened the app. It's showing enter 6 digit code. I have not been informed about an codes! Please look into the matter it's serious
Explain clearly what happen
You have to open http://ai2.appinventor.mit.edu to make apps. The app you're opening is Mit companion. It is used to live test your app.
Hello @Joyee, and welcome to the App Inventor Community! You must be talking about the MIT AI2 Companion, which is only an app that allows you to view your projects. To create an application of your own, please head over to the App Inventor site at ai2.appinventor.mit.edu.
Since this is not a Bug/Problem can we please have a moderator (@TIMAI2, @ChrisWard, @ABG, @Taifun 
) change this to the "App Inventor Help" category?
You can learn how to create apps here: Made with Code: Making Mobile Apps with App Inventor (mit.edu)
Hello Joyee.
The following explains how to enter the 6 digit code or to use the QR code. The procedure is described more fully in the first link below.
A dialog with a QR code will appear on your PC screen. On your device, launch the MIT App Companion app just as you would do any app. Then click the “Scan QR code” button on the Companion, and scan the code in the App Inventor window:
Within a few seconds, you should see the app you are building on your device. It will update as you make changes to your design and blocks, a feature called “live testing”.
This information is in the first link. The links show you how to make an app.
- Setup computer and phone/tablet or emulator for live testing as you build
- Preview the IDE
- Watch a beginner video tutorial to get started
Did this help?
Here is some additional information that will help you to code and make apps:
Here are some resources to help you learn to use the AI2 tools. A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook http://www.appinventor.org/book2 ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
There is a free programming course here http://www.appinventor.org/content/CourseInABox/Intro and the aia files for the projects in the book are here: http://www.appinventor.org/bookFiles
How to do a lot of basic things with App Inventor are described here: http://www.appinventor.org/content/howDoYou/eventHandling .
Also look here http://kio4.com/appinventor/index.htm and here http://www.imagnity.com/tutorial-index/ for more tutorials.
Learn about components http://ai2.appinventor.mit.edu/reference/components/
and visit the Library http://appinventor.mit.edu/explore/library Help>Library on the MENU