Hi Jen,
well, I'm trying to run my app within the creator. Please see the screenshot in the attachment, this is where I put the file "esri_runtime_qt_10_2.prf". To me, it looks like it is ment to be, after following your description.
The path "C:\Qt\Qt5.1.1\5.1.1\msvc2012_64\mkspecs\features" should be alright.
Are there any system variables that need to be set manually?
Thank you for your help!
Regards,
Günter