Correct address is Maria Van Bourgondiëstraat 30, 1000 Brussels. Easiest is to take the train to Brussel Noord / Bruxelles Nord (same station), and change trains to Brussel Luxemburg / Bruxelles Luxembourg. From there, you're a few minutes away from the embassy. I assume you'll be on the intercity from Oostende, which arrives at 4 minutes past the hour. There's a connection to Brussel Luxemburg at 12 minutes past the hour. The destination of that train is Liers. Brussel Luxemburg / Bruxelles Luxembourg will be the second stop. You don't need to buy an extra ticket for this train, your ticket Oostende - Brussels is valid to all Brussels stations.
Here's the google maps picture of the embassy:
On this picture, the station exit is the glass canopy at the bottom of the long square next to the European parliament, at the bottom of the picture.