I think you need the option B17 board to be fitted for IQ modulation. This is a large plug in board. Check to see if you already have it fitted.
If it isn't fitted, I'm not sure it's worth spending the time and money to get one. The IQ bandwidth is only about 2.5MHz. This is quite low.
Maybe watch this youtube video about fitting option B17. I've not watched it, but it probably will be useful to you.
There are lots of other options if you want to experiment with IQ modulation. If you want to do modulation and demodulation, then have a look at the various SDR radios available.