Currently the only way to enable customer portal users is to click the [Enable Customer Portal User] button on each individual contact.
To do this for all Contacts with an Account or for a large number of Contacts is extremely time-consuming.
The App should offer a way to “Mass Enable” Customer Portal users either through a button on the Contacts Related list or on a Contacts View that will enable Customer Portal Access for all selected Contacts. A page could be displayed where the common settings for the contacts can be set: License Type, Profile, etc.
Solution : Use the Data loader to Mass create “User” records. Add them to the correct UserType(CspLitePortal )Profile and link them to the correct Contact id : ContactID : 003Au00000JOoCaIAL
Account id : 001Au00000HysgZIAR
User ID : 0050A000001senzQAA
and Salesforce will do the rest.