How do I interact with the data in the default dashboards? Do I have to make a copy of the dashboard first?
Default dashboards are read-only, so you can not drill through, edit, or otherwise dive into the details of how they are made or what data they include. You can make some changes to the data in the dashboards by using the pre-built data and time filters they include. To learn more, see this article: Interacting with dashboards.
To make more substantial changes to a default dashboard, first you need to create a clone of the dashboard. Once the dashboard has been cloned, you can do a lot more as described in these articles: