I'm having difficulty adding story points to a project, How to enable that filed.
You should add the story points field to the screens for the Task issue type. You can find more info here how to add a custom field to a screen: https://confluence.atlassian.com/adminjiraserver/adding-a-custom-field-938847222.html
If you are trying to add it to issues not normally associated with a a software project you may have to do the following:
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