Hi Wahab,
If i understand correctly you are trying to integrate CA PAM with Vasco MFA.
Vasco has Identity key server(when i worked some time back) which is nothing but a radius server. So integration of CA PAM is just to add Vasco Identity key server IP address as a Radius server IP and secret key under PAM 3rd party Config section.
Now on the Vasco Identity key server you may need to register PAM IP address as a radius client(This you can find from their documentation)
Once done then assign the radius authentication method on the user group in CA PAM and test the authentication.
This should be a good starting point.
Let me know how it goes, Will be happy to help.