How do I configure this?

I tried to compile a .pro C++ proyect and got a message like this:
QMAKESPEC has not been set, so configuration cannot be deduced
error procesing projectfile: prueba.pro

what do I do? I'm using linux mandarke 9.0 (and have 9.2 but the menu panel crashes on 9.2) what is to "export" is it a command or just something you write to configure the QMAKESPEC? also is there something I can do so that when I try to qmake a file I don't have to write the whole path /usr/lib/qt3/bin/ qmake and is there a way to set -makefile to default?

Yeah - 'export QMAKESPEC=whatever' at a command prompt.

Not sure about the other questions but #2 might be taken care of by #1 or resolved similarly - 'export PATH=$PATH:/usr/lib/qt3/bin'. As far as '-makefile' it seems like something you could alias. All this can be done on the fly or put in ~/.bash_profile or ~/.bashrc to make it semi-permanent.

Sorry if this is missing the mark (IANAP), but this hadn't gotten replies, so maybe it'll help.