Hey PhamGiang, when creating a thread looking for help, please put into the title the subject you're looking for help on instead of just the word 'help'. This will help you by attracting others with knowledge on your subject. Otherwise your thread could be locked. If you have some time to kill, please go through the forum AUP to avoid any future infractions.
As for your question, it's very broad! For now I'm going to lock the thread and give you a chance to think over what type of apps you're interested in creating and create a new thread with a proper title and more specific details into your query.