Right now the app is handed out directly, before it reaches the stores. Download, open the file, and allow installing from this source when Android asks. If Play Protect warns you, choose Install anyway — it says that about any app outside the store.
Most phones from the last years use the 64-bit build above. Old or very cheap phones: 32-bit build.
Coming through TestFlight. Ask at support@whoswhere.net to be added when it’s ready.
You sign in with your Google account. No password, no separate registration. The app is open to anyone — it’s meant for people who know someone at AUBG.