How i can Change the HRHelpdesk User view fields read only once user submit the Helpdesk ticket

The client requirement is to make the fields read-only once the HR Help Desk user submits the ticket and later accesses it in edit mode.

Currently, when the employee opens the submitted ticket, all fields remain editable. The expectation is that the fields should no longer be editable after submission.

Tried the Read only from the form.. but it is not reflecting while i am trying to preview this..