Download Bulk load CSV Template from here: GET /alfresco/service/api/people/upload?format=csv
Example: (GET) http://127.0.0.1:8080/alfresco/service/api/people/upload?format=csv
This is the webscript definition for your reference:
<shortname>Create Users by using uploading of a CSV</shortname>
Allows an administrator to upload a CSV describing new users,
who will then have accounts created for them.
Note - if the CSV is uploaded OK, but there was a problem with
the contents or creating the users, you will receive a 200 status
code along with details of the problem.
<!-- Transactions are handled inside the webscript itself -->
If you have something very specific requirement for bulk loading users via CSV, which can't be met using the above given approaches, then you can choose to create your own webcript.