Upon opening the app for the first time you will be prompted to create a new wallet which alows you to send and receive regular on-chain transactions.
Every new wallet is generated randomly, so it is not tied to your device in any specific way. This is particularly important as it means that simply reinstalling the app and generating another wallet won’t restore your previous balance - you will get a completely new wallet instead!
There is, however, a simple way to preserve your balance across app reinstalls and even across different devices: you need to write down a mnemonic code once a new wallet is created.
Keeping your mnemonic code secure is very important. It is essentially a secret phrase comprising of 12 random words which is automatically provided by the app once a new wallet is created. Please remember: whoever knows your mnemonic code also fully controls your funds so it should be kept private and secure at all times.
Also, only the mnemonic code can get your balance back in case you lose your phone or simply uninstall the app by accident!
Next: Using Lightning wallet