I dont know the files, thats the main requirement of my project, there fore I must use QtFtp.
I do not think that this is absolutely true. Probably your thinking is FTP based, which makes it harder to get the basic idea of QNetworkAccessManager. The downloading mechanism looked strange to me in the beginning as well. Therefore, I had integrated the supplied QFtp module into Qt 5. FTP is basically technology of the 1980's. Command-driven stepping from folder to folder. Listing in between until you have navigated to the place where you had to go. This is emulated within the QFtp for Qt5.
Anyway the actual need of QFtp is more a philosophic discussion in my opinion.
I was able to compile it after the correction of a include error. What shall I do with the lot of output files now. Must I integrate this in my Qt current installation ?
QFtp is decrepated, but for compatibility Qt4 based applications you can add QtFtp
As already given in the first post follow the link and see the few steps.
The example is based on QNetworkAccessManager. However, you may use it directly or see how to create your required functionality based on QNetworkAccessManager
Your output should be basically 2 libs and 2 dlls (one for release and debug each). You can add them to your installation if you like.