I did this bicycle tour privatly. We went with Schnellbahn S7 in the afternoon to Fischamend (soon after Vienna Airport) and from there we went with the bicycle to Pottendorf. From there we took a train back
There are GPS files for this tour in the Internet:
But this route is little bit adventourous and goes over some meadows… I recommend to just follow the signs as much as possible (Fischa-Radweg).