The registration will open after the preliminaries have taken place.
The slots per institution for BAPC21 are limited. As there tends to be more teams than slots available, your institution can hold preliminary contests to determine which teams qualify for BAPC21. The preliminaries are expected to be held in the summer of 2021.
Registration for a preliminary at your institution is independent of a registration for BAPC21. Information on how to register a team representing your university is often arranged via your teaching staff or the study association representing either the mathematics or computer science department.