Before we get into the process of setting up your wallet, go over these basic security principles to make sure that you don't miss any important information and that you don't make any avoidable mistakes.
There are 3 security mechanisms that prevent you from accidental loss or theft of your Bitcoin:
Password and biometrics on Blue Wallet.
Seed backup recovery codes.
If you lose your BlueWallet
The Seed backup allows you to recover your Bitcoin wallets.
Your passphrase allows you to unlock the recovered Bitcoin wallets.
Both the seed backup and the passphrase are required to recover a lost wallet. If you lose the seed backup OR the passphrase, you will not be able to recover access to your bitcoin if you lose the BlueWallet app or your mobile device.
If someone steals your mobile device
The PIN protects unauthorized access to your BlueWallet, should it fall into the wrong hands.
If someone steals your BlueWallet and your password
They will be able to unlock the wallet, but they will not be able to spend funds without your biometrics.
If someone steals your seed backup recovery codes
They will not be able to recover your Bitcoin wallets without the passphrase.
If someone has access to both your seed backup your passphrase, they can steal your bitcoins! Do not keep a copy of them in the same place!