you should follow this complete tutorial where all the steps needed are listed:
The app was actually created using the same slide which was suggested above. However I'm not able to overwrite / write new script so that the students of college need not enter the the server address (skip the add site step) & directly enter the login credentials.
Note: I tried to manually enter the required page in Config.json file too.
I'm sorry but I don't get your problem, you say that you are not capable to edit the config.json file?
what error you get?