See https://tools.ietf.org/html/rfc4180, Common Format and MIME Type for Comma-Separated Values (CSV) Files.
The first line in the CSV file must contain the names as the column headers. Use the /CSV/headerNames API to get the list of header names.
Only one CSV import request can be running for the specified tenant.
If the default password is not specified, a random password will be generated and an email is sent with their password.
The maximum file size is 10MB.
When setting a value for the urn:ietf:params:scim:schemas:extension:ibm:2.0:User:linkedAccounts column, the value should be as follows: <externalId>@<realm>
When setting a value for the urn:ietf:params:scim:schemas:extension:enterprise:2.0:User:manager.value or urn:ietf:params:scim:schemas:extension:ibm:2.0:User:delegate columns, the value may be specified by name or ID. For example, testuser or 50GSYHD4C3.
Multiple-value attribute values are specified with a '|' delimiter which may be overridden with the optional multiValueDelimiter query parameter.
Attribute values that contain a special character (i.e. comma) must be enclosed in double quotes.
Entitlement required: manageUserGroups (Manage users and groups) or manageAllUserGroups (Synchronize users and groups) or manageUserStandardGroups (Manage users and standard groups).
Note: You only need one entitlement, but you can have more than one.
post https://{tenanturl}/v2.0/CSV/importUsers