The Flare desktop wallet uses 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 recovery phrase, click on "Settings" in the left-hand menu, then on the "Backup Phrase" button.
When you first open the Flare wallet, you have the option to recover a wallet using your 12 word seed phrase.
These 12 words can also be used in any BIP32/39 compliant wallet that supports NIX.
When you first create your wallet, you will be forced to choose a password. Use a strong password that only you know about.
You can change your password by clicking on "Settings" in the left-hand menu, then the "Reset Password" button.