Hi @Ravichandra Sreedharala and welcome to the community!
For a better analysis of your issue, I'm afraid more information is needed. What plan of Jira cloud are you on: free / standard / premium? Is your project company-managed or team-managed?
From what you are saying, I have the impression that you are struggling with a company-managed project. Project Admins do not have the permission to add/remove fields from screens: that is done by a Jira Administrator at a global level of the application. So, if that is the case, reach out to a Jira Admin in your organisation to help you achieve what you need.
For more information on permissions, do have a look at this support article
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