The exact address of your apartment is :
RUE MARCHE AU CHARBON 74 - 1000 BRUSSELS
But the keys and the luggage locker are in another building which is only a few dozen meters away:
RUE DES JARDINS DES OLIVES 17 - 1000 BRUSSELS

About the access to your apartment, please consult the FLAT PLAN in order to locate the access door, (to view it, click on the image)
You will find all the details to get there on the access page.,

At the end of your stay, please leave the keys in the P.O. Box with the surname "CARDENAS"

All the details concerning the keys, and the different doors in this link

At the end of your stay, please leave the keys in the post box with the surname "CARDENAS !!!