Jira Issue Field

[Atul Vig]

Hi, 

How do i add a custom field in jira when creating tickets, when you choose a user, it should show all open tickets from that user as well. 

Thank you, 

[Monika Rani]

Hi,

How do i add a custom field in jira when creating tickets

You can add the custom field from "Custom Fields" in the admin. You need Administrator access for this. If you have administrator access then go to "Setting->Issues->Fields->Custom Fields

Once you create the Custom field, associate it with the Screens. You can make it required or optional from the field configuration.

Go to your screens option and edit the create screen where you can mention the new custom field.

when you choose a user, it should show all open tickets from that user as well.

You can do this using JQL.

assignee=CurrentUser() AND status = "To Do"

[Tomas Gustavsson]

What you are asking, is not possible. 
Yes you can add a custom field, in Jira, but not while you are creating a ticket.

First you must create the custom field, then you can us that field when creating a ticket.

if you would like to see all issue for a specific user you need to do a search, please check under the issue menu, the filters in the picture below will filter out the issues that you have created. 

or you can us an JQL - Query e.g          reporter = currentUser() order by created DESC