You need administrator rights in Jira to perform the tasks on this page.
Once you have gone to the Custom fields page (see https://okapya.atlassian.net/wiki/spaces/CHKDOC5/pages/1738211329/Configuring+the+Checklist+custom+field), click See Templates to configure the templates that can be used with the checklist:
The following page will appear:
On this page, you can create, edit and delete templates for the checklist. For more information, see https://okapya.atlassian.net/wiki/spaces/CHKDOC5/pages/2384625699/Working+with+templates.