Wallet guardians is a feature to extra secure your wallet. Once set up, if you lose your secret key (skey) for whatever reasons, you will be able to use this feature to recover your skey.
How to setup Wallet Guardians
From the Assets tab go to Account tab as in the image below:
Next tap on Wallet & Security as in the image below:
Now tap on Wallet guardians as in the image below:
Now toggle Wallet guardians on, as in the image below:
You will be greeted with the screen below:
Enter your email address, set a password (not the same as your email password), re-type the password. Then tap on Create guardian.
Refer to the video tutorial below: