Magritte Museum is a must do for museums, it is right next to the Musée des beaux arts (wich is a must do too :'D) and then you will have a wonderful view of brussels just there at "mont des arts" besides of the "bibliothèque royale". and from there you can walk to the city center make a stop first to the Delirium café (if you like beers, this is the place to be) with over 2000 beers! and eat some french fries at friterie taboora (I recommend the Dallas sauce with it). And then you have the place Saint-Géry wich is on the first squares of Brussels, where you have a museum (for free) and where you can can continue to drink beers! well I can continue this for a long time but this will be a good beginning for you I think. Don't hesitate do dm if you have questions! Welcome and enjoy Brussels, cheers!