Mobile wallets use a 12 word seed phrase that will be displayed once you first open/create your wallet. Simply write down the list of words and store them in a safe place. It is strongly recommended that you do not store them electronically. Without these words (and in the proper order), recovery is not possible.
To view your seed phrase at any time, tap Menu.. Security Center.. Paper Key.
Security on mobile devices include both device level security along with in-app security options. Installing the app to a locked phone is highly recommended. Additionally, the app itself can further be secured with a 6 digit PIN and/or a Fingerprint ID. These in-app security settings can be found by tapping on Menu, then Security Center.