Normally there is no need to do so. Payment cardholders are automatically added to Vendor Verify when the payment cardholder feeds are sent in. However, this may not always happen timely, so a Vendor Verify Central Admin who also has the SSO Central Admin role can add the Vendor Verify User role to an employee in SSO.
To do give this role to an employee, go to SSO, change to the Central Admin role, search for the employee by UIN, select their record, go to the Roles tab, and add the role. See Assigning a Role in the SSO help system for more information.
To get the SSO Central Admin role assigned, see the SSO SoR page and follow the steps there.