Staff users must enable an external user's Contact record as a Customer User in order to access the Community Portal.
External users cannot be deleted. Instead, the user must be deactivated in order to restrict their access to the Community Portal. Make sure you have an Account and Contact created in order to Enable Community Portal Access for a Contact.
Enable Community Portal Access for a Contact:
Navigate to an existing Contact.
Click the Enable Customer User action. The User Edit page will open in Setup.
For an Account record, click the Manage External Account drop-down button and select Enable Partner.
From the User Edit page, in the General Information section:
Type or edit, the user's First Name, Last Name, and Email fields, if necessary. The Alias, Username, and Nickname fields auto-populate based upon the Email field.
Select the Customer Community User License and Customer Community User Profile from the User License and Profile picklists.
Click Save. When you return to the Contact's record, the Log in to Community as User action will be available. The available profiles depend on the assigned User License. Profiles contain settings and permissions, which control the functions the user can perform and field level visibility. The Contact, or Account, is enabled and can access the Community Portal.