Thanks for the post, glad to hear you were able to successfully integrate TestRail with Jira.
An API token for Jira is unique to each Jira user, so each user would need to create his/her own token and set their Jira credentials under ‘My Settings >Settings.’
You can have all Jira users use the same credentials by setting fallback values in the integration, however this would result in all new issues pushed to Jira appearing as if reported by this same user.
If you prefer to have each user submit issues and connect to Jira with their own accounts, individual credentials and API tokens would be needed.
Hope this helps,