How to use QLibrary?

[tbscope]

I dont know how to get the .h file from it.

I already have all the headers

I guess there's something fundamental you do not understand.

You have the DLL, that's ok.
You have the headers (.h file) that's great.

Now, include the header file in your own source code and link the dll with your program.
Something in the lines of LIBS += -lmpusbapi should be added to your .pro file