Matching wideband antenna with QUCS
Well, Qucs comes with a number of examples (File->Examples). One of them (filter_optimization.sch) shows how to set the optimization block...
Please make sure that ASCO is installed (http://asco.sourceforge.net/) 

IMHO, depending on the application you'll need to choose a lowpass or highpass LC matching network and then you'll need more or less LC stages depending on the bandwidth and the "jump" between the load impedance and Z0.

Hope it helps