There is metered parking on the streets in the Sablon district. As of March 2021, you can no longer park on the slopes in front of the Palace of Justice.
If you choose to access the church by public transportation, the nearest tram stop is "Petit Sablon" and the nearest metro stop is "Louise".
Additional Useful Information
The International Seventh-day Adventist Church is located on the 3rd floor of a 4 floor building. The building actually hosts three different Adventist churches and an office space for the Belgium-Luxembourg Federation and ADRA. The French-speaking congregation uses the basement, ground and first floor. The Flemmish congregation meets on the second floor and our International church is located on the 3rd floor. I know it sounds confusing, but don't hesitate to ask if you can't find your way!
The church is located on a narrow street, near to "Église Notre-Dame des Victoires au Sablon". The address above should lead you to the right place.