Brands have 14 days after the application deadline to accept any applicants.  Some brands will wait until all applications have been received before accepting. If you are accepted, you will hear from the brand as they will send you an agreement.  If you aren't accepted you will see the collaboration appear in your archived collaborations section when the deadline for the brand to accept applicants has passed.

Maximise your chances of being accepted by selling yourself when pitching - how you can help the brand raise exposure for their product(s)? Send them links of examples of how you have worked with brands previously, quality of content etc.