I can’t imagine being a normal consumer and wanting to set them up.
It’s quite simple on iOS. IIRC, when logging into the paypal website you get a prompt asking if you’d like to use passkeys. Accept that, then you get a keychain prompt asking if you’d like to make/use a passkey. Click continue and pass FaceID authentication, then you’re in with a passkey. For future logins you click the login with passkey and it faceIDs you in. It’s easy.