Czar of Midi
Since: Apr 04, 2002
Have you installed the drivers for the UX2 correctly? That is did you follow the installation instruction's perfectly?
If so, then you simply need to open the preferences or options section of Ableton for the audio portion and make sure the drivers for the UX2 are selected as the preferred audio input and output. Then once you arm a track you will select that driver as its input and output.
And you should not have had to purchase Ableton as it comes bundled with the UX2.