Within the first few weeks of your study a mentor will be assigned to you. The mentor will advise you with regards to the development of your professional skills (which includes assessment and training by the TU/e Skills Lab, see http://skillslabtue.nl/) and will help you in making the first choices for electives and in deciding which specialization best suits your interests.
At some point during your study your specialization will become clearer. This typically happens between the end of the second and fourth quarter. Your mentor will then help you in choosing new mentor from the group that best matches that specialization. The new mentor will then help you in selecting elective courses to prepare you for doing a master project in your area of interest and in selecting a trajectory for getting international experience (if needed). For more procedural aspects of your study such as obtaining approval of your study program and getting official permission to start your master project you should consult the study advisor.