What should I do with QML code ?
First, you need to ask questions which are (a) more precise, (b) more detailed, (c) less vague.
What do you trying to achieve? What have you tried so far? What went wrong? Is there any information you can provide (such as error messages which were returned) which might provide some clue as to what went wrong?
Second, you need to read the documentation. The documentation (in particular the Qt Quick Application Developer's Guide) contains a lot of information which should be useful to get developers up and running quickly. I'm not going to link you to it directly, as I think you should be able to find it on your own with a couple of minutes Googling or searching these forums (as I have posted the link here multiple times), if you find the Qt Project documentation landing page too complex to navigate directly - as I admit that it can be confusing at first.