If you've forgotten your PIN and can't login, you'll need to reinstall the Shoal app.
Once you've uninstalled, and then reinstalled the Shoal app, you'll be asked to log in using the email magic link and SMS OTP, and you'll then be prompted to set a new PIN.
If you're logged into the Shoal app and would like to update your PIN:
Tap the icon in the top left of the app
Scroll down and tap 'Logout'
Log in as normal using the email magic link and SMS OTP, and you'll then be able to set a new PIN