As long as you purchase your Rimowa in a WorldShop store or online at WorldShop.eu you’ll be eligible for the bonus miles. According to the terms and conditions not every Rimowa model is eligible. However, when I checked the promotion’s website, it showed over 80 Rimowa models as being qualified for the deal.
You don’t have to do anything special to qualify for the promo. Simply show your Miles & More card when purchasing the piece, or enter it during check out if ordering the piece through the WorldShop website.