You've spotted a job you like for which you think you are qualified. Time to take action.
First send an e-mail or letter with your CV to the employer. Your CV is your business card. You have to give it a lot of thought. You will find many tips for writing a good CV on the websites of VDAB, Actiris and Le Forem. Don't forget about the accompanying cover letter. Employers do read these things.
In the beginning you may have many rejections. But one day you'll get an interview. And make sure that you are ready. You can be well prepared for an interview, just like for an exam.