OK, I managed to do something ... I found a picture in nokia Qt Tutorials that the Build settings for the Desktop target should be like this:



Based on this, I managed to add the make command thing, like this:



The only difference now is that in my settings, the 'Toolchain' field is empty, and I don't know how to fix this ...

Also, at this stage when I try to compile my code for the Desktop target, I get the following error:

error: [debug/main.o] Error 1