And I get the error message: "collect2: ld returned 1 exit status"
Probably linker could not find needed files, could you show us your .pro file ?
If you have a line in your .pro
Qt Code: 
  1. LIBS += -l<dll name>
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then you should add
Qt Code: 
  1. LIBS += -L"path/to/dir/with/dll/file"
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in order to point the linker to directory where it should search for the referenced libraries.