You can use FishCoin today on both platforms — but the two routes are genuinely different, so this page says so rather than tidying them into a matching pair.
On iPhone there is an extra step, and it is Apple’s. FishCoin is not on the App Store yet, so it comes through TestFlight: install Apple’s TestFlight app first, tap the invitation, and FishCoin appears alongside your other apps. Anyone can join — there is no waiting list.
On Android there is no hoop to jump through. FishCoin is on Google Play now — open the listing and install it the way you install anything else. It updates by itself afterwards.
It is still a test build, so it is rougher than a finished app — that is the point of you having it. If Play tells you the app is not available for your device or account, this enrols you explicitly and then the listing will offer it: join the open test.