Hi,
As OpenCV is natively built with CMake, referencing it from a QMake-based project would involve non-trivial amount of manual settings edits.
Instead we would advise creating a CMake-based Qt projects (see this tutorial for details) and then referencing OpenCV using the regular find_package logic (see this tutorial).
If this is not an option, let us know and we can help you understand the logic behind the library paths and names so you could find the correct settings for the QMake project.