It is very simple. You can create a Restricted user with below query −
CREATE [RESTRICTED] USER <user_name> [<remote_identity_option>] [<password_option> ] [<external_ident> ] [<with_ident_opts> ] [<validity_specification> ] [<set_user_parameters> ] [<ldap_group_authorization>]
In above SQL query, you have to pass following parameters −
Specifies a database user in another tenant database as the remote identity of the database user being created.
Specifies the user password of the user being created.
Defines an external identification mechanism.
Defines an external identity that is used to authenticate the user.