I would like to add a custom field to upload screenshot or document related to the issue/test cases etc
There already exists an Attachments system field in Jira. Or is there something else that you are trying to accomplish?
It's a bit of a pain to do that - you have two options
1) edit core code (the stuff around the attachments screen) in order to do it, and thinking back to the other times this has come up, I don't remember anyone managing to do it satisfactorily.
2) write a plugin that provides an upload screen with your field, and you disable the built-in one. I've seen this done, but it was primitive and unfriendly compared with the built-in screen.
Of course, neither of these options are likely to happen for you - I don't think they'll be allowed in OnDemand.
Nic's suggestions are spot-on, and those options are not available if you are on an OnDemand instance.
You may want to take a look at the Bonfire plugin...
It looks like you're new here. Sign in or register to get started.