You can find the app in either the
Android store: https://play.google.com/store/apps/details?id=com.ea.gp.simsmobile&hl=en
or in the Apple store: https://itunes.apple.com/br/app/the-sims-mobile/id1144258115?l=en&mt=8
If you can't find them it could be your device isn't strong enough to play the game.
I do not work for EA
The game is releasing today and as @Phantomlover1717 explained, it will be available for iOS and Android.
It may take a bit to appear. I'd give it another try now and if it's still not showing for you, please, try again in a few hours.
Once it has released for everyone, if it's not showing for you, I'd try with another device as yours might not be compatible with the game.
I saw on instagram that the game is delayed and iOS is delayed. I saw that it will be released to everyone tomorrow 10am pst time. Any truth to that?