How to extend the UpmMember****p ?

All,

Anyone knows how to extend the UpmMember****p profile or how to configure 
another parameter in the CreateUser method ?

I need to create another information (like "pass****t number") when the
user 
creates the login (like register.aspx in StarterSite). 
I changed the profile (UserObject), but how the Member****p class know
about 
this new information ? 

Thanks!