Go to BananoVault, in the Manage Wallet settings, you can export your wallet as a QR CODE. When you do that, you will also see a link is generated which looks like:
https://vault.banano.cc/import-wallet#eyJhY2N...Fill the link with data from the puzzle and unlock the funds!
Another way would be to recognize the base64 format and decode to get a valid json file. The seed is encrypted using AES, find out how in the page source.