How I can add options like major, crash , severe, minor, text for the issues. Please help

[Anirudha]

I need to add bug saviority like major, minor, crash, ui, medium etc. 

How I can add them?

[DPKJ]

You can create a single select custom field, names Severity and options to it.

This explains how to add custom field to Jira issue - https://confluence.atlassian.com/adminjiraserver/adding-a-custom-field-938847222.html