You can register for courses via the new system bilsis.hacettepe.edu.tr. However, elective courses can only be viewed after selecting Makine Mühendisliği (ING DR) under the Ders ve Dönem İşlemleri > Ders Kayıt > Müfredat/Bölüm Dışı Dersler page. Be careful that MMÜ602 course is available to you in Makine Mühendisliği (ING YL). If you cannot see all courses in those pages, search for MMÜ in Ders Kod/Ad
See the file below as an example,