Clicking on the Design report link brings up the Report Designer (a credential is a special kind of report). Here you can add, remove and re-arrange fields. There are over a dozen field pipelines with hundreds of fields available in the credential designer here, which looks like (and is) identical to the report designer tool. See Advanced/Custom Reports for more information on how to use this tool.
Click on the To report manager link to save your filters and layout for later use. They'll be filed under the name you give, and will be available next time you click on the Saved link.