Client Portal access is enabled using a Contacts record of a CRM account.
Configuring Client Portal Access
Yes. Note: You can filter the Contacts page using the Has Client Portal Access option.
External User - Allows the client to view/edit their own profile and messages, as well as tickets assigned to them. External Manager - Allows the client to view/edit their own profile and messages. Also allows the client to view all of their account's tickets, contracts and invoices.