[Qt-creator] Using a .lib?

[Robert Caldecott]

I have created a project that consists of a Qt GUI and a C++ library.
The GUI depends on the library project, but fails to link as it cannot
find any of the library functions.  How do I tell the GUI project to
link with the .lib?  Do I simply add the .lib to the list of files?
If so, how do I have the project use the debug lib for debug builds
and the release lib for release builds?

I was hoping that the Project Dependency page would of taken care of
this for me.