How to REDEEM an INVITATION CODE in TESTFLIGHT APP?

here is ios apple test flight app where you can access some better versions of the apps so you can go to redeem section in top right and this is where you can enter a test flight invitation code to get invited uh to some pata version of of some app so that's basically what developers do they just release some testing version and then they share and invite or some invitation code and you need to have access to that and only then you will be able to to get to get access to this beta versions for example here's here's a racket and yeah this is how and then yeah you can just install this beta app or any app you want to have access to