customize second factor authentication on SAP login page

Hi guys,

hope you guys can provide some pointers for the problem

We are trying to do a second factor authentication one time pass [OTP] for our SAP login [Environment sap version 7.01.16].

We have follow the guide below and done and deployment our library [SDA format]

Create and Configure a Login Module - Developing Authentication Enhancements on the AS Java - SAP Library

but our question is where can we add an additional textbox for the OTP input from user in the login page?

thank you for reading

DX