You need administrator rights in Jira to perform the tasks on this page.
Like the Checklist custom field, the Checklist Proxy for Customer Portal custom field is configured on the Custom fields page. This page contains two links that enable you to further customize the behavior and appearance of your Customer Portal custom field by:
Editing the configuration scheme context (Customer Portal): Modify the configuration scheme context and choose the issue types and projects to which the configuration scheme will apply.
Editing parameters (Customer Portal): Customize the various settings.
To access the Custom fields page:
Go to Administration > Issues.
In the sidebar, go to Fields > Custom fields.
In the Actions column, click the menu icon for a specific custom field and click Configure.