Should you wish to enforce the use of password authentication across all iSecureLink Transfers platform wide, this can be set in the Options > Security > Secure Transfers tab, via the "Force use of password on Secure Transfers" setting:

If this setting is "Enabled" then users will not be able to change the authentication method on New iSecureLink Transfers and Authenticate via Email and Password will always be used.

If this setting is "Disabled" than users will be able to choose if they want to use just Email or Email and Password authentication.