To bulk create Jira users, select “Import users via CSV” from actions menu on “Jira Users” tab.
First, you need to set-up an API Key. To learn about how to generate an API Key, you can check How to create an API token?. The owner of the API Key should be allowed to create users. You can prefer to save your API Key, or you can import users without saving it. If you do not save it, you need to enter it again while importing users the next time.
After setting up your API key, import a CSV file that contains the emails of your users. You can find a sample CSV for bulk creating users below.