How to create supplier login base on the supplier name not supplier email address

How to create supplier login base on the supplier name not supplier email address

we are using isupplier portal, supplier life cycle management, sourcing,

Buyer tried to register a new supplier and the supplier login base on 'supplier name' not 'supplier email address' through supplier management > Register new supplier>

enter supplier information> actions: Send Pre-Qualification and questionare.> Send supplier registration invitation to suppler by email.

After supplier response to invitation, then approved by buyer, the supplier login account is created but base on supplier email account.