Do I have to formally apply to the BSE?
You can apply for a position for a spot in the Fast Track program at the BSE at the beginnning of your Master's. If you are accepted, you will benefit from the Workshops and Seminars offered by the BSE.
However, it is not necessary to apply for a spot at the BSE's Fast Track program, in order to take part in the Seminars. You have access to the Seminars offered in the Fast Track through your Master's in Public Economics. The courses you attend at the BSE can be credited to both your Master's and future PhD.