Ableton can search for VSTs in the preference section but it should have found it anyway because Ableton will scan any newly added plugins automatically on start up and you should be able to use them straight away without any issues whatsoever. I use Ableton Lite 8 sometimes for tracking, my son uses it all the time, my mate uses Live9 and together we have never had this issue. The only trouble using SDx with Ableton is that, as far as I know or I couldn't figure it out, you can't use multiple outs from SDx to Ableton to further process the individual sounds which is why I jumped to Logic but that's another thread I guess.